the following table summarizes our revenues by product type for the years ended december 31 , 2018 , 2017 and 2016 : replace_table_token_7_th ev parts during the year ended december 31 , 2018 , our revenue from the sale of ev parts was $ 99,099,312 , representing an increase of $ 1,743,484 or 1.8 % from $ 97,355,828 for the year ended december 31 , 2017 and a decrease of $ 20,980,000 or 17.5 % from $ 120,079,312 for the year ended december 31 , 2016 , respectively . our revenue for the year ended december 31 , 2018 primarily consisted of the sales of battery packs , body parts , ev drive motors , ev controllers , air conditioning units and other auto parts for use in the ev products manufactured by the jv company , which accounted for 88.1 % of total sales . among total sales for the year ended december 31 , 2018 , approximately 75.6 % were related to the sale of battery packs . in compliance with the regulations of the chinese auto industry , we hold the necessary production licenses to manufacture the battery packs exclusively used in ev products manufactured by the jv company . besides the sale of battery packs , approximately 3.5 % of total sales were related to sales of ev controllers , approximately 2.7 % of the total sales were related to sales of air conditioning units , approximately 3.5 % of total sales were related to sales of ev drive motors and approximately 2.8 % of total sales were related to sales of body parts and other auto parts . during the year ended december 31 , 2018 and 2017 , our revenues from the sale of ev parts to the jv company accounted approximately 43.3 % and 90.4 % of our total net revenue for the year , respectively . the ev parts we sold to the jv company were used in manufacturing pure ev products by the jv company 's subsidiaries . ev products our revenue from the sale of ev products for the fiscal year 2018 and 2017 was $ 0 , representing a decrease of $ 3,718,291 or 100 % from $ 3,718,291 for the year ended december 31 , 2016. pursuant to the jv agreement , production of ev products was completely transferred to the jv company at the end of 2014 , but the company retained the right to sell ev products that remained in stock . the company completed sales of ev products in stock in 2016. the company currently primarily focuses on manufacturing and supplying ev parts to the jv company and third parties for the production of evs . off-road vehicles during the year ended december 31 , 2018 , our revenues from the sale of off-road vehicles including go-karts , all-terrain vehicles ( “ atvs ” ) , and others , were $ 13,339,516 , representing an increase of $ 7,889,723 or 144.8 % from $ 5,449,793 for the year ended december 31 , 2017 , and an increase of $ 7,645,106 or 134.3 % from $ 5,694,410 for the year ended december 31 , 2016. the increase in revenue of off-road vehicles was largely due to additional sales from sc autosports , which became our wholly-owned subsidiary in the u.s. in july 2018. our off-road vehicles business line accounted for approximately 11.9 % of our total net revenue for the year ended december 31 , 2018. of our off-road vehicle revenue , our atv business accounted for approximately 8.5 % of our total net revenue and our go-kart business accounted for approximately 3.3 % of our total net revenue . 28 the following table shows the breakdown of our net revenues : replace_table_token_8_th cost of goods sold cost of goods sold for the year ended december 31 , 2018 was $ 92,191,383 , representing an increase of $ 3,729,951 , or 4.2 % , from $ 88,461,432 for the year ended december 31 , 2017 and a decrease of $ 19,578,814 , or 17.5 % , from $ 111,770,197 for the year ended december 31 , 2016. the change was primarily due to the corresponding increase in sales from 2017 and decrease in sales from 2016. please refer to the gross profit section below for product margin analysis . gross profit our margins by product for the past three years are as set forth below : replace_table_token_9_th 29 gross profit for the year ended december 31 , 2018 was $ 20,247,445 , as compared to $ 14,344,189 for the year ended december 31 , 2017 , and $ 17,721,816 for the year ended december 31 , 2016 , representing an increase of $ 5,903,256 or 41.2 % from 2017 and an increase of $ 2,525,629 or 14.3 % from 2016. the increases were primarily attributable to the increased margin in 2018 as compared to that in 2017 and 2016. our gross margin for the year ended december 31 , 2018 , was 18.0 % , compared to 14.0 % for the year ended december 31 , 2017 , and 13.7 % for the year ended december 31 , 2016. the increase in our gross margin as compared to 2017 and 2016 was mainly due to the higher gross margin from off-road vehicle sales of sc autosports , a result of its effective procurement of inventories at discounted prices , as well as increased gross margin from sales of battery packs . story_separator_special_tag adjustments to reduce the cost of inventory to its net realizable value are made , if required , for estimated excess , obsolescence , or impaired balances . when inventories are sold , their carrying amount is charged to expense in the year in which the revenue is recognized . write-downs for declines in net realizable value or for losses of inventories are recognized as an expense in the year the impairment or loss occurs . there were $ 840,701 and $ 620,919 of decline in net realizable value of inventory for the years ended of december 31 , 2018 and 2017 , respectively , due to our provision for slow moving inventory . although we believe that there is little likelihood that actual results will differ materially from our current estimates , if customer demand for our products decreases significantly in the near future , or if the financial condition of our customers deteriorates in the near future , we could realize significant write downs for slow-moving inventories or uncollectible accounts receivable . policy affecting recognition of revenue our revenue recognition policy plays a key role in our consolidated financial statements . we recognize revenue when goods or services are transferred to customers in an amount that reflects the consideration which we expect to receive in exchange for those goods or services . in determining when and how revenue is recognized from contracts with customers , we perform the following five-step analysis : ( i ) identification of contract with customer; ( ii ) determination of performance obligations; ( iii ) measurement of the transaction price; ( iv ) allocation of the transaction price to the performance obligations; and ( v ) recognition of revenue when ( or as ) we satisfy each performance obligation . we generate revenue through the sale of ev products , ev parts and off-road vehicles and our revenue recognition policies for our ev products , ev parts and off-road vehicles are the same . the revenue is recognized at a point in time once we have determined that the customer has obtained control over the product . control is typically deemed to have been transferred to the customer when the performance obligation is fulfilled , usually at the time of delivery , at the net sales price ( transaction price ) . estimates of variable consideration , such as volume discounts and rebates , are determined , reviewed and revised periodically by management . revenue is recognized net of any taxes collected from customers , which are subsequently remitted to governmental authorities . shipping and handling costs for product shipments occur prior to the customer obtaining control of the goods are accounted for as fulfillment costs rather than separate performance obligations and recorded as sales and marketing expenses . policy affecting options , warrants and convertible notes our stock option cost is recorded in accordance with asc 718 and asc 505. the fair value of stock options is estimated using the black-scholes-merton model . our expected volatility assumption is based on the historical volatility of our stock . the expected life assumption is primarily based on the expiration date of the option . the risk-free interest rate for the expected term of the option is based on the u.s. treasury yield curve in effect at the time of grant . stock option expense recognition is based on awards expected to vest . there were no estimated forfeitures . asc standards require forfeitures to be estimated at the time of grant and revised in subsequent periods , if necessary , if actual forfeitures differ from those estimates . 37 our warrant costs are recorded in liabilities and equities , respectively , in accordance with asc 480 , asc 505 and asc 815. the fair value of a warrant , which is classified as a liability , is estimated using the binomial tree model and the lattice valuation model . our expected volatility assumption is based on the historical volatility of our common stock . the expected life assumption is primarily based on the expiration date of the warrant . the risk-free interest rate for the expected term of the warrant is based on the u.s. treasury yield curve in effect at the time of measurement . our warrants , which are freestanding derivatives classified as liabilities on the balance sheet , are measured at fair value on each reporting date , with decreases in fair value recognized in earnings and increases in fair values recognized in expenses . the fair value of equity-based warrants , which are not considered derivatives under asc 815 , is estimated using the black-scholes -merton model . our expected volatility assumption is based on the historical volatility of our common stock . the expected life assumption is primarily based on the expiration date of the warrant . the risk-free interest rate for the expected term of the option is based on the u.s. treasury yield curve in effect at the time of grant . in accordance with asc 815 , the conversion feature of the convertible notes is separated from the debt instrument and accounted for separately as a derivative instrument . on the date the convertible notes are issued , the conversion feature is recorded as a liability at its fair value , and future decreases in fair value are recognized in earnings while increases in fair values are recognized in expenses . we used the black-scholes -merton option-pricing model to obtain the fair value of the conversion feature . the expected volatility assumption is based on the historical volatility of our common stock . the expected life assumption is primarily based on the expiration date of the conversion features . the risk-free interest rate for the expected term of the conversion features is based on the u.s. treasury yield curve in effect at the time of measurement . warranty liability most of our non-ev products ( “ legacy products ” ) are exported out of china to

cash flow for the year ended december 31 , 2018 , cash provided in operating activities was $ 13,587,621 , as compared to cash used in operating activities of $ 3,214,471 for the year ended december 31 , 2017 , and cash used in operating activities of $ 49,526,543 for the year ended december 31 , 2016. our operating cash inflows include cash received primarily from sales of our ev parts and off-road vehicles . these cash inflows are offset largely by cash paid primarily to our suppliers for production materials and parts used in our manufacturing process , operation expenses , employee compensation , and interest expenses on our financings . the major operating activities that provided cash for the year ended december 31 , 2018 were an increase of accounts payable of $ 137,390,139 , ( net of assignment of notes receivable from unrelated parties to suppliers to settle accounts payable of $ 31,347,383 , assignment of notes receivable from jv company and related parties to suppliers to settle accounts payable of $ 77,107,835 , settlement of accounts payable with notes payables of $ 31,039,932 , reversal of construction in progress and accounts payable of $ 8,029,198 , reclassification of overpaid accounts payable of $ 16,826 to advances to suppliers , and replacement of notes payables with accounts payable of $ 10,582,651 ) , and an increase of other payables and accrued liabilities of $ 60,736,669 ( net of assignment of notes receivable from unrelated parties to supplier to settle other payable of $ 28,636,652 and assignment of notes receivablefrom jv company and related parties to supplier to settle other payable of $ 34,242,433 ) .


 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 flow for the year ended december 31 , 2018 , cash provided in operating activities was $ 13,587,621 , as compared to cash used in operating activities of $ 3,214,471 for the year ended december 31 , 2017 , and cash used in operating activities of $ 49,526,543 for the year ended december 31 , 2016. our operating cash inflows include cash received primarily from sales of our ev parts and off-road vehicles . these cash inflows are offset largely by cash paid primarily to our suppliers for production materials and parts used in our manufacturing process , operation expenses , employee compensation , and interest expenses on our financings . the major operating activities that provided cash for the year ended december 31 , 2018 were an increase of accounts payable of $ 137,390,139 , ( net of assignment of notes receivable from unrelated parties to suppliers to settle accounts payable of $ 31,347,383 , assignment of notes receivable from jv company and related parties to suppliers to settle accounts payable of $ 77,107,835 , settlement of accounts payable with notes payables of $ 31,039,932 , reversal of construction in progress and accounts payable of $ 8,029,198 , reclassification of overpaid accounts payable of $ 16,826 to advances to suppliers , and replacement of notes payables with accounts payable of $ 10,582,651 ) , and an increase of other payables and accrued liabilities of $ 60,736,669 ( net of assignment of notes receivable from unrelated parties to supplier to settle other payable of $ 28,636,652 and assignment of notes receivablefrom jv company and related parties to supplier to settle other payable of $ 34,242,433 ) .
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 Suspicious Activity Report : the following table summarizes our revenues by product type for the years ended december 31 , 2018 , 2017 and 2016 : replace_table_token_7_th ev parts during the year ended december 31 , 2018 , our revenue from the sale of ev parts was $ 99,099,312 , representing an increase of $ 1,743,484 or 1.8 % from $ 97,355,828 for the year ended december 31 , 2017 and a decrease of $ 20,980,000 or 17.5 % from $ 120,079,312 for the year ended december 31 , 2016 , respectively . our revenue for the year ended december 31 , 2018 primarily consisted of the sales of battery packs , body parts , ev drive motors , ev controllers , air conditioning units and other auto parts for use in the ev products manufactured by the jv company , which accounted for 88.1 % of total sales . among total sales for the year ended december 31 , 2018 , approximately 75.6 % were related to the sale of battery packs . in compliance with the regulations of the chinese auto industry , we hold the necessary production licenses to manufacture the battery packs exclusively used in ev products manufactured by the jv company . besides the sale of battery packs , approximately 3.5 % of total sales were related to sales of ev controllers , approximately 2.7 % of the total sales were related to sales of air conditioning units , approximately 3.5 % of total sales were related to sales of ev drive motors and approximately 2.8 % of total sales were related to sales of body parts and other auto parts . during the year ended december 31 , 2018 and 2017 , our revenues from the sale of ev parts to the jv company accounted approximately 43.3 % and 90.4 % of our total net revenue for the year , respectively . the ev parts we sold to the jv company were used in manufacturing pure ev products by the jv company 's subsidiaries . ev products our revenue from the sale of ev products for the fiscal year 2018 and 2017 was $ 0 , representing a decrease of $ 3,718,291 or 100 % from $ 3,718,291 for the year ended december 31 , 2016. pursuant to the jv agreement , production of ev products was completely transferred to the jv company at the end of 2014 , but the company retained the right to sell ev products that remained in stock . the company completed sales of ev products in stock in 2016. the company currently primarily focuses on manufacturing and supplying ev parts to the jv company and third parties for the production of evs . off-road vehicles during the year ended december 31 , 2018 , our revenues from the sale of off-road vehicles including go-karts , all-terrain vehicles ( “ atvs ” ) , and others , were $ 13,339,516 , representing an increase of $ 7,889,723 or 144.8 % from $ 5,449,793 for the year ended december 31 , 2017 , and an increase of $ 7,645,106 or 134.3 % from $ 5,694,410 for the year ended december 31 , 2016. the increase in revenue of off-road vehicles was largely due to additional sales from sc autosports , which became our wholly-owned subsidiary in the u.s. in july 2018. our off-road vehicles business line accounted for approximately 11.9 % of our total net revenue for the year ended december 31 , 2018. of our off-road vehicle revenue , our atv business accounted for approximately 8.5 % of our total net revenue and our go-kart business accounted for approximately 3.3 % of our total net revenue . 28 the following table shows the breakdown of our net revenues : replace_table_token_8_th cost of goods sold cost of goods sold for the year ended december 31 , 2018 was $ 92,191,383 , representing an increase of $ 3,729,951 , or 4.2 % , from $ 88,461,432 for the year ended december 31 , 2017 and a decrease of $ 19,578,814 , or 17.5 % , from $ 111,770,197 for the year ended december 31 , 2016. the change was primarily due to the corresponding increase in sales from 2017 and decrease in sales from 2016. please refer to the gross profit section below for product margin analysis . gross profit our margins by product for the past three years are as set forth below : replace_table_token_9_th 29 gross profit for the year ended december 31 , 2018 was $ 20,247,445 , as compared to $ 14,344,189 for the year ended december 31 , 2017 , and $ 17,721,816 for the year ended december 31 , 2016 , representing an increase of $ 5,903,256 or 41.2 % from 2017 and an increase of $ 2,525,629 or 14.3 % from 2016. the increases were primarily attributable to the increased margin in 2018 as compared to that in 2017 and 2016. our gross margin for the year ended december 31 , 2018 , was 18.0 % , compared to 14.0 % for the year ended december 31 , 2017 , and 13.7 % for the year ended december 31 , 2016. the increase in our gross margin as compared to 2017 and 2016 was mainly due to the higher gross margin from off-road vehicle sales of sc autosports , a result of its effective procurement of inventories at discounted prices , as well as increased gross margin from sales of battery packs . story_separator_special_tag adjustments to reduce the cost of inventory to its net realizable value are made , if required , for estimated excess , obsolescence , or impaired balances . when inventories are sold , their carrying amount is charged to expense in the year in which the revenue is recognized . write-downs for declines in net realizable value or for losses of inventories are recognized as an expense in the year the impairment or loss occurs . there were $ 840,701 and $ 620,919 of decline in net realizable value of inventory for the years ended of december 31 , 2018 and 2017 , respectively , due to our provision for slow moving inventory . although we believe that there is little likelihood that actual results will differ materially from our current estimates , if customer demand for our products decreases significantly in the near future , or if the financial condition of our customers deteriorates in the near future , we could realize significant write downs for slow-moving inventories or uncollectible accounts receivable . policy affecting recognition of revenue our revenue recognition policy plays a key role in our consolidated financial statements . we recognize revenue when goods or services are transferred to customers in an amount that reflects the consideration which we expect to receive in exchange for those goods or services . in determining when and how revenue is recognized from contracts with customers , we perform the following five-step analysis : ( i ) identification of contract with customer; ( ii ) determination of performance obligations; ( iii ) measurement of the transaction price; ( iv ) allocation of the transaction price to the performance obligations; and ( v ) recognition of revenue when ( or as ) we satisfy each performance obligation . we generate revenue through the sale of ev products , ev parts and off-road vehicles and our revenue recognition policies for our ev products , ev parts and off-road vehicles are the same . the revenue is recognized at a point in time once we have determined that the customer has obtained control over the product . control is typically deemed to have been transferred to the customer when the performance obligation is fulfilled , usually at the time of delivery , at the net sales price ( transaction price ) . estimates of variable consideration , such as volume discounts and rebates , are determined , reviewed and revised periodically by management . revenue is recognized net of any taxes collected from customers , which are subsequently remitted to governmental authorities . shipping and handling costs for product shipments occur prior to the customer obtaining control of the goods are accounted for as fulfillment costs rather than separate performance obligations and recorded as sales and marketing expenses . policy affecting options , warrants and convertible notes our stock option cost is recorded in accordance with asc 718 and asc 505. the fair value of stock options is estimated using the black-scholes-merton model . our expected volatility assumption is based on the historical volatility of our stock . the expected life assumption is primarily based on the expiration date of the option . the risk-free interest rate for the expected term of the option is based on the u.s. treasury yield curve in effect at the time of grant . stock option expense recognition is based on awards expected to vest . there were no estimated forfeitures . asc standards require forfeitures to be estimated at the time of grant and revised in subsequent periods , if necessary , if actual forfeitures differ from those estimates . 37 our warrant costs are recorded in liabilities and equities , respectively , in accordance with asc 480 , asc 505 and asc 815. the fair value of a warrant , which is classified as a liability , is estimated using the binomial tree model and the lattice valuation model . our expected volatility assumption is based on the historical volatility of our common stock . the expected life assumption is primarily based on the expiration date of the warrant . the risk-free interest rate for the expected term of the warrant is based on the u.s. treasury yield curve in effect at the time of measurement . our warrants , which are freestanding derivatives classified as liabilities on the balance sheet , are measured at fair value on each reporting date , with decreases in fair value recognized in earnings and increases in fair values recognized in expenses . the fair value of equity-based warrants , which are not considered derivatives under asc 815 , is estimated using the black-scholes -merton model . our expected volatility assumption is based on the historical volatility of our common stock . the expected life assumption is primarily based on the expiration date of the warrant . the risk-free interest rate for the expected term of the option is based on the u.s. treasury yield curve in effect at the time of grant . in accordance with asc 815 , the conversion feature of the convertible notes is separated from the debt instrument and accounted for separately as a derivative instrument . on the date the convertible notes are issued , the conversion feature is recorded as a liability at its fair value , and future decreases in fair value are recognized in earnings while increases in fair values are recognized in expenses . we used the black-scholes -merton option-pricing model to obtain the fair value of the conversion feature . the expected volatility assumption is based on the historical volatility of our common stock . the expected life assumption is primarily based on the expiration date of the conversion features . the risk-free interest rate for the expected term of the conversion features is based on the u.s. treasury yield curve in effect at the time of measurement . warranty liability most of our non-ev products ( “ legacy products ” ) are exported out of china to

