the warrants have a five-year term and are exercisable beginning 181 days after their issue date . the aggregate net purchase price for the securities sold in the 2020 private placement was approximately $ 20.3 million . the transaction was completed on march 19 , 2020. all outstanding shares of series a preferred stock automatically converted into shares 6.6 million shares of our common stock on june 16 , 2020 upon receipt of stockholder approval at our annual meeting of stockholders held on june 16 , 2020. for additional information on the 2020 private placement , see note 1 “ nature of operations—the 2020 private placement ” in the notes to our consolidated financial statements included elsewhere in this report . 79 equity purchase agreement with lincoln park on june 16 , 2020 , we entered into the equity purchase agreement with lincoln park , which provides that , upon the terms and subject to the conditions and limitations set forth therein , we may sell to lincoln park up to $ 31.0 million of shares of our common stock pursuant to our shelf registration statement . the purchase price of shares of common stock related to a future sale will be based on the then prevailing market prices of such shares at the time of sales as described in the equity purchase agreement . concurrently with entering into the equity purchase agreement , we also entered into a registration rights agreement with lincoln park , pursuant to which we agreed to provide lincoln park with certain registration rights related to the shares issued under the equity purchase agreement ( the “ registration rights agreement ” ) . see ‘ ‘ —liquidity and capital resources `` below . in 2020 , we issued and sold to lincoln park 3.0 million shares of our common stock , with 0.2 million of these shares being issued to lincoln park as a commitment fee in connection with entering into the equity purchase agreement ( the “ commitment shares ” ) . the total value of the commitment shares of $ 0.6 million together with the issuance costs of $ 0.1 million were recorded as deferred issuance costs in the consolidated balance sheet . these costs will be amortized into consolidated statements of stockholders ' equity proportionally based on proceeds received during the period and the expected total proceeds to be raised over the term of the equity purchase agreement . the net proceeds from shares issuance as of december 31 , 2020 were $ 8.4 million . the equity purchase agreement will enhance our balance sheet and financial condition to support our future growth initiatives . december 2020 public offering on december 24 , 2020 , we sold in a public offering 11,250,000 shares of common stock and warrants to purchase up to 5,625,000 shares of common stock at a combined offering price to the public of $ 2.00 per share and accompanying warrants . the warrants have an exercise price of $ 2.50 per share of common stock , are exercisable immediately , and expire in five years from the date of issuance . total net proceeds generated by the december 2020 public offering was $ 20.5 million . main street priority lending program term loan on december 8 , 2020 , we executed a loan and security agreement , a promissory note , and related documents for a loan in the aggregate amount of $ 50.0 million for which cnb will serve as a lender pursuant to the main street priority loan facility ( the “ mslp loan ” ) . on december 9 , 2020 , the mslp loan had been funded and the transaction was closed . the mslp note has a term of five years and bears interest at a rate per annum equal to 30-day libor plus 3 % . we used the proceeds from the mslp loan to repay in full an outstanding balance of $ 3.2 million under the cnb loan agreement and partially repay our obligation under the madryn credit agreement of $ 43.6 million ( including principal of $ 42.5 million ) . the rest of the outstanding debt under the madryn credit agreement was converted into secured convertible promissory notes in the aggregate amount of $ 26.7 million . for additional information regarding the mslp loan and mslp note , see the “ risk factors ” and note 10 “ main street term loan ” to our consolidated financial statements included elsewhere in this report . products and services we derive revenue from the sale of products and services . product revenue includes revenue from the following : the sale , including traditional sales and subscription-based sales , of systems , inclusive of the main console and control software and applicators ( referred to as system revenue ) ; marketing supplies and kits ; consumables and disposables ; service revenue ; and replacement applicators/handpieces . service revenue includes revenue derived from our verografters technician services , our 2two5 internal advertising agency , and our extended warranty service contracts provided to our existing customers . our 2two5 internal advertising agency services were discontinued in the third quarter of 2020. these revenues were not material to our 2020 results . 80 systems are sold through our subscription model , or through traditional sales contracts directly and through distributors . we generate recurring monthly revenue under our subscription-based business model and from traditional system sales . venus concept ltd. commenced a subscription-based model in north america in 2011 , and approximately 46 % and 51 % of our aesthetic systems were sold under the subscription model in the years ended december 31 , 2020 and 2019 , respectively . we have launched our subscription model in targeted international markets in which we operate directly . story_separator_special_tag as a result of the global economic turmoil that has resulted from covid-19 , many of our customers experienced difficulty in making timely payments or payments at all during the pandemic under their subscription agreements and we experienced a significant reduction in the collection of accounts receivable from our subscription customers across markets in the first half of 2020. we entered into repayment arrangements with the majority of non-paying customers , and as government lockdown and shelter in place orders were lifted we experienced a significant improvement in collections as businesses reopened . notwithstanding the improvement in our cash collections , we determined that an allowance for doubtful accounts be established for those accounts that closed their operations , defaulted or were struggling to make consistent monthly payments . as a result , in addition to our regular allowance for doubtful accounts , we recorded a covid-19 related bad debt charge of $ 11.1 million in 2020 which represents 12 % of the gross outstanding accounts receivable as of december 31 , 2020. in our largest subscription markets we collected approximately 60 % of our billings in march 2020 , 30 % in april 2020 , 35 % in may 2020 , 60 % in june 2020 , 104 % in july 2020 , 97 % in august 2020 , and 98 % in september 2020 . the improvement in collection trends , starting from may 2020 and continuing through to september , is directly correlated to business re-openings and our collection efforts . through the third quarter of 2020 , we continued to proactively manage the collection of accounts receivables and have made repayment arrangements with the majority of our non-paying subscription customers to either defer collection or to collect a reduced amount , with the expectation of full collection as business activities resume . as a result of implementing repayment arrangements with the majority of our non-paying subscription customers , the majority of these customers recommenced payments in those jurisdictions where shelter-in-place orders were lifted , and their businesses reopened . our systems are equipped with monthly activation codes , and non-paying customers will not be provided with codes unless overdue balances are cleared , or they make a repayment arrangement with us . notwithstanding the collection improvements experienced through our third quarter results , in october 2020 our customers , in most of the markets we operate in , experienced the emergence of a second wave of covid-19 cases resulting in a reinstatement , or partial reinstatement , of government lockdown and shelter in place restrictions . many of the customers that agreed to repayment arrangements were negatively impacted , forced to temporarily close their operations again and could not honor their repayment arrangements . in our largest subscription markets we collected approximately 86 % of our billings in october 2020 , 86 % of our billings in november 2020 , and 87 % in december 2020. we estimate that 14 % of our pre-covid-19 customers in north america were forced to close their operations either temporarily or permanently . as a result , in addition to our regular allowance for doubtful accounts , we recorded an additional covid-19 related bad debt charge of $ 5.4 million in the fourth quarter of fiscal 2020. for the full fiscal year ended december 31 , 2020 , we estimate the total covid-19 related bad debt charge to be approximately $ 11.1 million , of which approximately $ 3.0 million related to accounts that had fully defaulted and the balance relates to accounts that are at risk but fully provided for . we remain fully focused on reactivating collections with those at risk accounts that that have struggled through the pandemic but showing signs of viability . as of december 31 , 2020 , our allowance for doubtful accounts stands at $ 18.5 million and represents that represents 20 % of the gross outstanding accounts receivable as of this date . with the recent approvals and successful rollout of covid-19 vaccines , we have experienced an improvement in our collection experience . the relative success of the second wave lockdown measures , combined with vaccination rollout plans has resulted in reduced lockdown restrictions in most of the markets we operate in . our collection experience has also improved in the post year-end period , with collections in our largest subscription markets averaging 87 % of our billings in january 2021 , 92 % of our billings in february 2021 , and approximately 97 % of our billings through march 2021. we will continue our pro-active management of collections and will revisit our allowance for doubtful accounts during the next quarter . 85 mitigation efforts . we are focused on continuing to mitigate the impacts of the covid-19 pandemic on our business to the extent possible . our mitigation efforts include the following : accounts receivables collections initiatives . we have made repayment arrangements with the majority of our non-paying subscription customers to collect temporarily reduced monthly payments where possible and or deferred amounts in expectation of full collection as business activities continue to resume . we modified our payment arrangements with these subscription customers such that past due amounts are scheduled to be repaid over a three to six-month period . we made further adjustments with the emergence of the second covid-19 wave , where payment arrangements from the first wave were not fully honored but we continue to work with these customers to formulate revised payment plans . based on our interactions and arrangements in place thus far with our subscription customers , the majority of them have recommenced , or plan to recommence payments in those jurisdictions where shelter-in-place orders have been lifted and their businesses reopened . while the repayment arrangements and improvements in collections activities made thus far have resulted in our cash collections rate approaching pre-covid-19 levels , we may not be successful in collecting all outstanding amounts . cost reduction initiatives . our efforts

cash flows the following table summarizes our cash flows for the years indicated : replace_table_token_8_th 98 cash flows from operating activities for the year ended december 31 , 2020 , cash used in operating activities consisted of a net loss of $ 82.8 million and an investment in net operating assets of $ 7.7 million , partially offset by non-cash operating expenses of $ 61.9 million . the investment in net operating assets was primary attributable to a decrease in inventories of $ 1.0 million , decrease in other current assets of $ 2.4 million , decrease in other long-term assets of $ 0.2 million , increase in trade payables of $ 3.0 million , increase in unearned interest income of $ 1.9 million and increase in other long-term liabilities of $ 0.5 million . this was partially offset by a decrease in accounts receivable of $ 0.1 million , decrease in prepaid expenses by $ 0.2 million and increase in accrued expenses and other current liabilities of $ 0.9 million . the non-cash operating expenses consisted mainly of a goodwill impairment charge of $ 27.5 million , a provision for bad debts of $ 15.2 million , depreciation and amortization of $ 4.8 million , stock-based compensation expense of $ 2.1 million , provision for inventory obsolescence of $ 0.6 million , loss on debt extinguishment of $ 2.9 million , loss on sale of subsidiaries of $ 2.5 million , loss on disposal of property and equipment of $ 0.2 million , deferred tax benefit of $ 0.4 million , a change in the fair value of the earn-out liability for the purchase of neograft of $ 0.3 million , interest on convertible promissory notes of $ 0.1 million and finance expenses of $ 6.1 million .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```cash flows the following table summarizes our cash flows for the years indicated : replace_table_token_8_th 98 cash flows from operating activities for the year ended december 31 , 2020 , cash used in operating activities consisted of a net loss of $ 82.8 million and an investment in net operating assets of $ 7.7 million , partially offset by non-cash operating expenses of $ 61.9 million . the investment in net operating assets was primary attributable to a decrease in inventories of $ 1.0 million , decrease in other current assets of $ 2.4 million , decrease in other long-term assets of $ 0.2 million , increase in trade payables of $ 3.0 million , increase in unearned interest income of $ 1.9 million and increase in other long-term liabilities of $ 0.5 million . this was partially offset by a decrease in accounts receivable of $ 0.1 million , decrease in prepaid expenses by $ 0.2 million and increase in accrued expenses and other current liabilities of $ 0.9 million . the non-cash operating expenses consisted mainly of a goodwill impairment charge of $ 27.5 million , a provision for bad debts of $ 15.2 million , depreciation and amortization of $ 4.8 million , stock-based compensation expense of $ 2.1 million , provision for inventory obsolescence of $ 0.6 million , loss on debt extinguishment of $ 2.9 million , loss on sale of subsidiaries of $ 2.5 million , loss on disposal of property and equipment of $ 0.2 million , deferred tax benefit of $ 0.4 million , a change in the fair value of the earn-out liability for the purchase of neograft of $ 0.3 million , interest on convertible promissory notes of $ 0.1 million and finance expenses of $ 6.1 million .
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 Suspicious Activity Report : the warrants have a five-year term and are exercisable beginning 181 days after their issue date . the aggregate net purchase price for the securities sold in the 2020 private placement was approximately $ 20.3 million . the transaction was completed on march 19 , 2020. all outstanding shares of series a preferred stock automatically converted into shares 6.6 million shares of our common stock on june 16 , 2020 upon receipt of stockholder approval at our annual meeting of stockholders held on june 16 , 2020. for additional information on the 2020 private placement , see note 1 “ nature of operations—the 2020 private placement ” in the notes to our consolidated financial statements included elsewhere in this report . 79 equity purchase agreement with lincoln park on june 16 , 2020 , we entered into the equity purchase agreement with lincoln park , which provides that , upon the terms and subject to the conditions and limitations set forth therein , we may sell to lincoln park up to $ 31.0 million of shares of our common stock pursuant to our shelf registration statement . the purchase price of shares of common stock related to a future sale will be based on the then prevailing market prices of such shares at the time of sales as described in the equity purchase agreement . concurrently with entering into the equity purchase agreement , we also entered into a registration rights agreement with lincoln park , pursuant to which we agreed to provide lincoln park with certain registration rights related to the shares issued under the equity purchase agreement ( the “ registration rights agreement ” ) . see ‘ ‘ —liquidity and capital resources `` below . in 2020 , we issued and sold to lincoln park 3.0 million shares of our common stock , with 0.2 million of these shares being issued to lincoln park as a commitment fee in connection with entering into the equity purchase agreement ( the “ commitment shares ” ) . the total value of the commitment shares of $ 0.6 million together with the issuance costs of $ 0.1 million were recorded as deferred issuance costs in the consolidated balance sheet . these costs will be amortized into consolidated statements of stockholders ' equity proportionally based on proceeds received during the period and the expected total proceeds to be raised over the term of the equity purchase agreement . the net proceeds from shares issuance as of december 31 , 2020 were $ 8.4 million . the equity purchase agreement will enhance our balance sheet and financial condition to support our future growth initiatives . december 2020 public offering on december 24 , 2020 , we sold in a public offering 11,250,000 shares of common stock and warrants to purchase up to 5,625,000 shares of common stock at a combined offering price to the public of $ 2.00 per share and accompanying warrants . the warrants have an exercise price of $ 2.50 per share of common stock , are exercisable immediately , and expire in five years from the date of issuance . total net proceeds generated by the december 2020 public offering was $ 20.5 million . main street priority lending program term loan on december 8 , 2020 , we executed a loan and security agreement , a promissory note , and related documents for a loan in the aggregate amount of $ 50.0 million for which cnb will serve as a lender pursuant to the main street priority loan facility ( the “ mslp loan ” ) . on december 9 , 2020 , the mslp loan had been funded and the transaction was closed . the mslp note has a term of five years and bears interest at a rate per annum equal to 30-day libor plus 3 % . we used the proceeds from the mslp loan to repay in full an outstanding balance of $ 3.2 million under the cnb loan agreement and partially repay our obligation under the madryn credit agreement of $ 43.6 million ( including principal of $ 42.5 million ) . the rest of the outstanding debt under the madryn credit agreement was converted into secured convertible promissory notes in the aggregate amount of $ 26.7 million . for additional information regarding the mslp loan and mslp note , see the “ risk factors ” and note 10 “ main street term loan ” to our consolidated financial statements included elsewhere in this report . products and services we derive revenue from the sale of products and services . product revenue includes revenue from the following : the sale , including traditional sales and subscription-based sales , of systems , inclusive of the main console and control software and applicators ( referred to as system revenue ) ; marketing supplies and kits ; consumables and disposables ; service revenue ; and replacement applicators/handpieces . service revenue includes revenue derived from our verografters technician services , our 2two5 internal advertising agency , and our extended warranty service contracts provided to our existing customers . our 2two5 internal advertising agency services were discontinued in the third quarter of 2020. these revenues were not material to our 2020 results . 80 systems are sold through our subscription model , or through traditional sales contracts directly and through distributors . we generate recurring monthly revenue under our subscription-based business model and from traditional system sales . venus concept ltd. commenced a subscription-based model in north america in 2011 , and approximately 46 % and 51 % of our aesthetic systems were sold under the subscription model in the years ended december 31 , 2020 and 2019 , respectively . we have launched our subscription model in targeted international markets in which we operate directly . story_separator_special_tag as a result of the global economic turmoil that has resulted from covid-19 , many of our customers experienced difficulty in making timely payments or payments at all during the pandemic under their subscription agreements and we experienced a significant reduction in the collection of accounts receivable from our subscription customers across markets in the first half of 2020. we entered into repayment arrangements with the majority of non-paying customers , and as government lockdown and shelter in place orders were lifted we experienced a significant improvement in collections as businesses reopened . notwithstanding the improvement in our cash collections , we determined that an allowance for doubtful accounts be established for those accounts that closed their operations , defaulted or were struggling to make consistent monthly payments . as a result , in addition to our regular allowance for doubtful accounts , we recorded a covid-19 related bad debt charge of $ 11.1 million in 2020 which represents 12 % of the gross outstanding accounts receivable as of december 31 , 2020. in our largest subscription markets we collected approximately 60 % of our billings in march 2020 , 30 % in april 2020 , 35 % in may 2020 , 60 % in june 2020 , 104 % in july 2020 , 97 % in august 2020 , and 98 % in september 2020 . the improvement in collection trends , starting from may 2020 and continuing through to september , is directly correlated to business re-openings and our collection efforts . through the third quarter of 2020 , we continued to proactively manage the collection of accounts receivables and have made repayment arrangements with the majority of our non-paying subscription customers to either defer collection or to collect a reduced amount , with the expectation of full collection as business activities resume . as a result of implementing repayment arrangements with the majority of our non-paying subscription customers , the majority of these customers recommenced payments in those jurisdictions where shelter-in-place orders were lifted , and their businesses reopened . our systems are equipped with monthly activation codes , and non-paying customers will not be provided with codes unless overdue balances are cleared , or they make a repayment arrangement with us . notwithstanding the collection improvements experienced through our third quarter results , in october 2020 our customers , in most of the markets we operate in , experienced the emergence of a second wave of covid-19 cases resulting in a reinstatement , or partial reinstatement , of government lockdown and shelter in place restrictions . many of the customers that agreed to repayment arrangements were negatively impacted , forced to temporarily close their operations again and could not honor their repayment arrangements . in our largest subscription markets we collected approximately 86 % of our billings in october 2020 , 86 % of our billings in november 2020 , and 87 % in december 2020. we estimate that 14 % of our pre-covid-19 customers in north america were forced to close their operations either temporarily or permanently . as a result , in addition to our regular allowance for doubtful accounts , we recorded an additional covid-19 related bad debt charge of $ 5.4 million in the fourth quarter of fiscal 2020. for the full fiscal year ended december 31 , 2020 , we estimate the total covid-19 related bad debt charge to be approximately $ 11.1 million , of which approximately $ 3.0 million related to accounts that had fully defaulted and the balance relates to accounts that are at risk but fully provided for . we remain fully focused on reactivating collections with those at risk accounts that that have struggled through the pandemic but showing signs of viability . as of december 31 , 2020 , our allowance for doubtful accounts stands at $ 18.5 million and represents that represents 20 % of the gross outstanding accounts receivable as of this date . with the recent approvals and successful rollout of covid-19 vaccines , we have experienced an improvement in our collection experience . the relative success of the second wave lockdown measures , combined with vaccination rollout plans has resulted in reduced lockdown restrictions in most of the markets we operate in . our collection experience has also improved in the post year-end period , with collections in our largest subscription markets averaging 87 % of our billings in january 2021 , 92 % of our billings in february 2021 , and approximately 97 % of our billings through march 2021. we will continue our pro-active management of collections and will revisit our allowance for doubtful accounts during the next quarter . 85 mitigation efforts . we are focused on continuing to mitigate the impacts of the covid-19 pandemic on our business to the extent possible . our mitigation efforts include the following : accounts receivables collections initiatives . we have made repayment arrangements with the majority of our non-paying subscription customers to collect temporarily reduced monthly payments where possible and or deferred amounts in expectation of full collection as business activities continue to resume . we modified our payment arrangements with these subscription customers such that past due amounts are scheduled to be repaid over a three to six-month period . we made further adjustments with the emergence of the second covid-19 wave , where payment arrangements from the first wave were not fully honored but we continue to work with these customers to formulate revised payment plans . based on our interactions and arrangements in place thus far with our subscription customers , the majority of them have recommenced , or plan to recommence payments in those jurisdictions where shelter-in-place orders have been lifted and their businesses reopened . while the repayment arrangements and improvements in collections activities made thus far have resulted in our cash collections rate approaching pre-covid-19 levels , we may not be successful in collecting all outstanding amounts . cost reduction initiatives . our efforts

