backlog includes ( i ) unissued task orders and unexercised option years , to the extent their issuance or exercise is probable , as well as ( ii ) contract awards , to the extent we believe contract execution and funding is probable . the following table summarizes the value of our backlog at the respective dates presented ( in thousands ) : replace_table_token_10_th ( 1 ) as presented in the company 's form s-1/a filed on april 29 , 2019 , funded backlog for the federal solutions segment was overstated by $ 893.8 million with a corresponding understatement in unfunded backlog . there was no impact on total federal solutions backlog or total backlog for parsons corporation . ( 2 ) difference between our backlog of $ 8.0 billion and our rupo of $ 5.0 billion , each as of december 31 , 2019 , is due to ( i ) unissued task orders and unexercised option years , to the extent their issuance or exercise is probable , as well as ( ii ) contract awards , to the extent we believe contract execution and funding is probable . our backlog includes orders under contracts that in some cases extend for several years . for example , the u.s. congress generally appropriates funds for our u.s. federal government customers on a yearly basis , even though their contracts with us may call for performance that is expected to take a number of years to complete . as a result , our federal contracts typically are only partially funded at any point during their term . all or some of the work to be performed under the contracts may remain unfunded unless and until the u.s. congress makes subsequent appropriations and the procuring agency allocates funding to the contract . we expect to recognize $ 2.8 billion of our funded backlog at december 31 , 2019 as revenues in the following twelve months . however , our u.s. federal government customers may cancel their contracts with us at any time through a termination for convenience or may elect to not exercise option periods under such contracts . in the case of a termination for convenience , we would not receive anticipated future revenues , but would generally be permitted to recover all or a portion of our incurred costs and fees for work performed . see “ risk factors—risks relating to our business—we may not realize the full value of our backlog , which may result in lower than expected revenue . ” the changes in backlog in our federal solutions segment between fiscal 2018 and fiscal 2019 included contributions of $ 0.3 billion from business acquisitions . backlog in our critical infrastructure segment , in fiscal 2019 , was impacted primarily by a number of potential awards being pushed out to 2020. our backlog will fluctuate in any given period based on the volume of awards issued in comparison to the revenue generated from our existing contracts . 53 book-to-bill book-to-bill is the ratio of total awards to total revenue recorded in the same period . our management believes our book-to-bill ratio is a useful indicator of our potential future revenue growth in that it measures the rate at which we are generating new awards compared to the company 's current revenue . to drive future revenue growth , our goal is for the level of awards in a given period to exceed the revenue booked . a book-to-bill ratio greater than 1.0 indicates that awards generated in a given period exceeded the revenue recognized in the same period , while a book-to-bill ratio of less than 1.0 indicates that awards generated in such period were less than the revenue recognized in such period . the following table sets forth the book-to-bill ratio for the periods presented below : replace_table_token_11_th factors and trends affecting our results of operations we believe that the financial performance of our business and our future success are dependent upon many factors , including those highlighted in this section . our operating performance will depend upon many variables , including the success of our growth strategies and the timing and size of investments and expenditures that we choose to undertake , as well as market growth and other factors that are not within our control . government spending changes in the relative mix of government spending and areas of spending growth , with shifts in priorities on homeland security , intelligence , defense-related programs , infrastructure and urbanization , and continued increased spending on technology and innovation , including cybersecurity , artificial intelligence , connected communities and physical infrastructure , could impact our business and results of operations . cost-cutting and efficiency initiatives , current and future budget restrictions , spending cuts and other efforts to reduce government spending could cause our government customers to reduce or delay funding or invest appropriated funds on a less consistent basis or not at all , and demand for our solutions or services could diminish . furthermore , any disruption in the functioning of government agencies , including as a result of government closures and shutdowns , could have a negative impact on our operations and cause us to lose revenue or incur additional costs due to , among other things , our inability to deploy our staff to customer locations or facilities as a result of such disruptions . federal budget uncertainty there is uncertainty around the timing , extent , nature and effect of congressional and other u.s. government actions to address budgetary constraints , caps on the discretionary budget for defense and non-defense departments and agencies , and the ability of congress to determine how to allocate the available budget authority and pass appropriations bills to fund both u.s. government departments and agencies that are , and those that are not , subject to the caps . story_separator_special_tag indirect , general and administrative expenses fiscal year ended variance ( u.s. dollars in thousands ) december 31 , 2018 december 31 , 2019 dollar percent indirect , general and administrative expenses $ 597,410 $ 781,408 $ 183,998 30.8 % indirect , general and administrative expenses ( “ ig & a ” ) for the years ended december 31 , 2018 and december 31 , 2019 include $ 16.5 million and $ 65.7 million , respectively , of compensation cost related to equity-based awards that primarily settle in cash . cash settled awards are remeasured to an updated fair value at each reporting period until the award is settled . compensation cost is trued-up at each reporting period for changes in fair value pro-rated for the portion of the requisite service period rendered . the significant increase in compensation cost related to these cash settled equity-based awards for the year ended december 31 , 2019 is due to the significant difference in the fair value of a share of the company 's common stock under parsons esop valuation at december 31 , 2018 compared to the fair value of a share of the company 's common stock in the public market at december 31 , 2019. see item 5 of part ii for ranges in the share price of the company 's common stock since the consummation of the ipo and “ note 19— fair value of financial instruments ” in the notes to our consolidated financial statements included elsewhere in this annual report on form 10-k for a description of how the esop share value is determined . see “ note 1— description of operations ” in the notes to our consolidated financial statements included elsewhere in this annual report on form 10-k for more detail regarding the company 's ipo . the plans in which these awards were granted have been frozen and the company does not currently intend to grant any further cash settled equity-based awards . excluding the compensation costs discussed above , ig & a for the years ended december 31 , 2018 and december 31 , 2019 were $ 580.9 million and $ 715.7 million , respectively . the increase in ig & a of $ 134.8 million for the year ended december 31 , 2019 when compared to the corresponding period last year was primarily due to our federal solutions segment , most of which is related to additional expenses of $ 47.8 million from business acquisitions , $ 50.9 million from the amortization of intangible assets related to our acquisitions and $ 11.2 million in acquisition-related expenses . the remaining increase of $ 24.9 million is related to additional bid and proposal costs and an increase in corporate functional group costs . total other income ( expense ) replace_table_token_14_th 60 i nterest income is related to interest earned on cash balances held . i nterest expense is primarily due to debt related to our business acquisitions . during the year ended december 31 , 2019 , the company 's term loan of $ 150 million was paid off and the amount of debt outstanding under the company 's revolving credit facility was reduced . the amounts in other income ( expense ) , net are primarily related to transaction gains and losses on foreign currency transactions and sublease income . the amount presented in gain associated with claim on long-term contract for the year ended december 31 , 2018 relates to a lawsuit against a joint venture in which the company is the managing partner . see “ results of operations—other income and expenses ” above for a description of this matter , which was resolved in favor of the company on june 13 , 2018. income tax ( expense ) benefit fiscal year ended variance ( u.s. dollars in thousands ) december 31 , 2018 december 31 , 2019 dollar percent income tax ( expense ) benefit $ ( 20,367 ) $ 69,886 $ 90,253 443.1 % income tax expense decreased in fiscal 2019 primarily due to the revaluation of our deferred tax assets and liabilities as a result of our conversion from “ s ” corporation to a “ c ” corporation , partially offset by the impact of the increase in overall pre-tax earnings subject to taxation as a result of our conversion to a “ c ” corporation . as described in “ note 14 – income taxes , ” in the notes to our consolidated financial statements included elsewhere in this annual report on form 10-k , in connection with the company 's ipo on may 8 , 2019 , the company converted from an “ s ” corporation to a “ c ” corporation . on a pro forma basis , if the company had been taxed as a “ c ” corporation for the year ended december 31 , 2018 and december 31 , 2019 , the pro forma effective tax rate would have been 28.77 % and 36.89 % , respectively , and the company 's pro forma income tax expense would have been $ 74.8 million and $ 24.8 million , respectively . the most significant item contributing to the change in the effective tax rate relates to a change in jurisdictional earnings . the difference between the statutory u.s. federal income tax rate of 21 % and the effective tax rate for the year ended december 31 , 2019 primarily relates to foreign earnings which are subject to foreign income taxes at rates that exceed the u.s. income tax rate . the termination of the “ s ” corporation status was treated as a change in tax status for accounting standards codification 740 , income taxes . these rules require that the deferred tax effects of a change in tax status to be recorded to income from continuing operations on the date the “ s ” corporation status terminates . through the year ended december 31 , 2019 , the company recorded

cash flows cash received from customers , either from the payment of invoices for work performed or for advances in excess of revenue recognized , is our primary source of cash . we generally do not begin work on contracts until funding is appropriated by the customers . billing timetables and payment terms on our contracts vary based on a number of factors , including whether the contract type is cost-plus , time-and-materials , or fixed-price . we generally bill and collect cash more frequently under cost-plus and time-and-materials contracts , as we are authorized to bill as the costs are incurred or work is performed . in contrast , we may be limited to bill certain fixed-price contracts only when specified milestones , including deliveries , are achieved . a number of our contracts may provide for performance-based payments , which allow us to bill and collect cash prior to completing the work . billed accounts receivable represents amounts billed to clients that have not been collected . unbilled accounts receivable represents amounts where the company has a present contractual right to bill but an invoice has not been issued to the customer at the period-end date . accounts receivable is the principal component of our working capital and is generally driven by revenue growth . accounts receivable includes billed and unbilled amounts . the total amount of our accounts receivable can vary significantly over time , but is generally sensitive to revenue levels . we experience delays in collections from time to time from middle east customers . net days sales outstanding , which we refer to as net dso , is calculated by dividing ( i ) accounts receivable ( net of project accruals , billings in excess of revenue and accounts payable ) by ( ii ) average revenue per day ( calculated by dividing trailing twelve months revenue by the number of days in that period ) . we focus on collecting outstanding receivables to reduce net dso and working capital .


 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 cash received from customers , either from the payment of invoices for work performed or for advances in excess of revenue recognized , is our primary source of cash . we generally do not begin work on contracts until funding is appropriated by the customers . billing timetables and payment terms on our contracts vary based on a number of factors , including whether the contract type is cost-plus , time-and-materials , or fixed-price . we generally bill and collect cash more frequently under cost-plus and time-and-materials contracts , as we are authorized to bill as the costs are incurred or work is performed . in contrast , we may be limited to bill certain fixed-price contracts only when specified milestones , including deliveries , are achieved . a number of our contracts may provide for performance-based payments , which allow us to bill and collect cash prior to completing the work . billed accounts receivable represents amounts billed to clients that have not been collected . unbilled accounts receivable represents amounts where the company has a present contractual right to bill but an invoice has not been issued to the customer at the period-end date . accounts receivable is the principal component of our working capital and is generally driven by revenue growth . accounts receivable includes billed and unbilled amounts . the total amount of our accounts receivable can vary significantly over time , but is generally sensitive to revenue levels . we experience delays in collections from time to time from middle east customers . net days sales outstanding , which we refer to as net dso , is calculated by dividing ( i ) accounts receivable ( net of project accruals , billings in excess of revenue and accounts payable ) by ( ii ) average revenue per day ( calculated by dividing trailing twelve months revenue by the number of days in that period ) . we focus on collecting outstanding receivables to reduce net dso and working capital .
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 Suspicious Activity Report : backlog includes ( i ) unissued task orders and unexercised option years , to the extent their issuance or exercise is probable , as well as ( ii ) contract awards , to the extent we believe contract execution and funding is probable . the following table summarizes the value of our backlog at the respective dates presented ( in thousands ) : replace_table_token_10_th ( 1 ) as presented in the company 's form s-1/a filed on april 29 , 2019 , funded backlog for the federal solutions segment was overstated by $ 893.8 million with a corresponding understatement in unfunded backlog . there was no impact on total federal solutions backlog or total backlog for parsons corporation . ( 2 ) difference between our backlog of $ 8.0 billion and our rupo of $ 5.0 billion , each as of december 31 , 2019 , is due to ( i ) unissued task orders and unexercised option years , to the extent their issuance or exercise is probable , as well as ( ii ) contract awards , to the extent we believe contract execution and funding is probable . our backlog includes orders under contracts that in some cases extend for several years . for example , the u.s. congress generally appropriates funds for our u.s. federal government customers on a yearly basis , even though their contracts with us may call for performance that is expected to take a number of years to complete . as a result , our federal contracts typically are only partially funded at any point during their term . all or some of the work to be performed under the contracts may remain unfunded unless and until the u.s. congress makes subsequent appropriations and the procuring agency allocates funding to the contract . we expect to recognize $ 2.8 billion of our funded backlog at december 31 , 2019 as revenues in the following twelve months . however , our u.s. federal government customers may cancel their contracts with us at any time through a termination for convenience or may elect to not exercise option periods under such contracts . in the case of a termination for convenience , we would not receive anticipated future revenues , but would generally be permitted to recover all or a portion of our incurred costs and fees for work performed . see “ risk factors—risks relating to our business—we may not realize the full value of our backlog , which may result in lower than expected revenue . ” the changes in backlog in our federal solutions segment between fiscal 2018 and fiscal 2019 included contributions of $ 0.3 billion from business acquisitions . backlog in our critical infrastructure segment , in fiscal 2019 , was impacted primarily by a number of potential awards being pushed out to 2020. our backlog will fluctuate in any given period based on the volume of awards issued in comparison to the revenue generated from our existing contracts . 53 book-to-bill book-to-bill is the ratio of total awards to total revenue recorded in the same period . our management believes our book-to-bill ratio is a useful indicator of our potential future revenue growth in that it measures the rate at which we are generating new awards compared to the company 's current revenue . to drive future revenue growth , our goal is for the level of awards in a given period to exceed the revenue booked . a book-to-bill ratio greater than 1.0 indicates that awards generated in a given period exceeded the revenue recognized in the same period , while a book-to-bill ratio of less than 1.0 indicates that awards generated in such period were less than the revenue recognized in such period . the following table sets forth the book-to-bill ratio for the periods presented below : replace_table_token_11_th factors and trends affecting our results of operations we believe that the financial performance of our business and our future success are dependent upon many factors , including those highlighted in this section . our operating performance will depend upon many variables , including the success of our growth strategies and the timing and size of investments and expenditures that we choose to undertake , as well as market growth and other factors that are not within our control . government spending changes in the relative mix of government spending and areas of spending growth , with shifts in priorities on homeland security , intelligence , defense-related programs , infrastructure and urbanization , and continued increased spending on technology and innovation , including cybersecurity , artificial intelligence , connected communities and physical infrastructure , could impact our business and results of operations . cost-cutting and efficiency initiatives , current and future budget restrictions , spending cuts and other efforts to reduce government spending could cause our government customers to reduce or delay funding or invest appropriated funds on a less consistent basis or not at all , and demand for our solutions or services could diminish . furthermore , any disruption in the functioning of government agencies , including as a result of government closures and shutdowns , could have a negative impact on our operations and cause us to lose revenue or incur additional costs due to , among other things , our inability to deploy our staff to customer locations or facilities as a result of such disruptions . federal budget uncertainty there is uncertainty around the timing , extent , nature and effect of congressional and other u.s. government actions to address budgetary constraints , caps on the discretionary budget for defense and non-defense departments and agencies , and the ability of congress to determine how to allocate the available budget authority and pass appropriations bills to fund both u.s. government departments and agencies that are , and those that are not , subject to the caps . story_separator_special_tag indirect , general and administrative expenses fiscal year ended variance ( u.s. dollars in thousands ) december 31 , 2018 december 31 , 2019 dollar percent indirect , general and administrative expenses $ 597,410 $ 781,408 $ 183,998 30.8 % indirect , general and administrative expenses ( “ ig & a ” ) for the years ended december 31 , 2018 and december 31 , 2019 include $ 16.5 million and $ 65.7 million , respectively , of compensation cost related to equity-based awards that primarily settle in cash . cash settled awards are remeasured to an updated fair value at each reporting period until the award is settled . compensation cost is trued-up at each reporting period for changes in fair value pro-rated for the portion of the requisite service period rendered . the significant increase in compensation cost related to these cash settled equity-based awards for the year ended december 31 , 2019 is due to the significant difference in the fair value of a share of the company 's common stock under parsons esop valuation at december 31 , 2018 compared to the fair value of a share of the company 's common stock in the public market at december 31 , 2019. see item 5 of part ii for ranges in the share price of the company 's common stock since the consummation of the ipo and “ note 19— fair value of financial instruments ” in the notes to our consolidated financial statements included elsewhere in this annual report on form 10-k for a description of how the esop share value is determined . see “ note 1— description of operations ” in the notes to our consolidated financial statements included elsewhere in this annual report on form 10-k for more detail regarding the company 's ipo . the plans in which these awards were granted have been frozen and the company does not currently intend to grant any further cash settled equity-based awards . excluding the compensation costs discussed above , ig & a for the years ended december 31 , 2018 and december 31 , 2019 were $ 580.9 million and $ 715.7 million , respectively . the increase in ig & a of $ 134.8 million for the year ended december 31 , 2019 when compared to the corresponding period last year was primarily due to our federal solutions segment , most of which is related to additional expenses of $ 47.8 million from business acquisitions , $ 50.9 million from the amortization of intangible assets related to our acquisitions and $ 11.2 million in acquisition-related expenses . the remaining increase of $ 24.9 million is related to additional bid and proposal costs and an increase in corporate functional group costs . total other income ( expense ) replace_table_token_14_th 60 i nterest income is related to interest earned on cash balances held . i nterest expense is primarily due to debt related to our business acquisitions . during the year ended december 31 , 2019 , the company 's term loan of $ 150 million was paid off and the amount of debt outstanding under the company 's revolving credit facility was reduced . the amounts in other income ( expense ) , net are primarily related to transaction gains and losses on foreign currency transactions and sublease income . the amount presented in gain associated with claim on long-term contract for the year ended december 31 , 2018 relates to a lawsuit against a joint venture in which the company is the managing partner . see “ results of operations—other income and expenses ” above for a description of this matter , which was resolved in favor of the company on june 13 , 2018. income tax ( expense ) benefit fiscal year ended variance ( u.s. dollars in thousands ) december 31 , 2018 december 31 , 2019 dollar percent income tax ( expense ) benefit $ ( 20,367 ) $ 69,886 $ 90,253 443.1 % income tax expense decreased in fiscal 2019 primarily due to the revaluation of our deferred tax assets and liabilities as a result of our conversion from “ s ” corporation to a “ c ” corporation , partially offset by the impact of the increase in overall pre-tax earnings subject to taxation as a result of our conversion to a “ c ” corporation . as described in “ note 14 – income taxes , ” in the notes to our consolidated financial statements included elsewhere in this annual report on form 10-k , in connection with the company 's ipo on may 8 , 2019 , the company converted from an “ s ” corporation to a “ c ” corporation . on a pro forma basis , if the company had been taxed as a “ c ” corporation for the year ended december 31 , 2018 and december 31 , 2019 , the pro forma effective tax rate would have been 28.77 % and 36.89 % , respectively , and the company 's pro forma income tax expense would have been $ 74.8 million and $ 24.8 million , respectively . the most significant item contributing to the change in the effective tax rate relates to a change in jurisdictional earnings . the difference between the statutory u.s. federal income tax rate of 21 % and the effective tax rate for the year ended december 31 , 2019 primarily relates to foreign earnings which are subject to foreign income taxes at rates that exceed the u.s. income tax rate . the termination of the “ s ” corporation status was treated as a change in tax status for accounting standards codification 740 , income taxes . these rules require that the deferred tax effects of a change in tax status to be recorded to income from continuing operations on the date the “ s ” corporation status terminates . through the year ended december 31 , 2019 , the company recorded

