in 2017 , cash flows provided by operations increased $ 160 million , primarily due to an increase in net income after non-cash adjustments , including the impact of the enactment of the tcja , and an increase in cash flows from working capital .the main factors contributing to the net income increase are described in the 201cconsolidated results of operations 201d section and include higher operating revenues , partially offset by higher income taxes due to a $ 125 million re-measurement charge resulting from the impact of the change in the federal tax rate on the company 2019s deferred income taxes from the enactment of the tcja .the increase in non-cash activities was mainly attributable to the increase in deferred income taxes , as mentioned above , and an increase in depreciation and amortization due to additional utility plant placed in service .the change in working capital was principally due to ( i ) the timing of accounts payable and accrued liabilities , including the accrual recorded during 2016 for the binding global agreement in principle to settle claims associated with the freedom industries chemical spill in west virginia , ( ii ) a decrease in unbilled revenues as a result of our military services group achieving significant capital project milestones during 2016 , and ( iii ) a change in other current assets and liabilities , including the decrease in other current assets associated with the termination of our four forward starting swap agreements and timing of payments clearing our cash accounts .the company expects to make pension contributions to the plan trusts of up to $ 31 million in 2019 .in addition , we estimate that contributions will amount to $ 32 million , $ 29 million , $ 29 million and $ 29 million in 2020 , 2021 , 2022 and 2023 , respectively .actual amounts contributed could change materially from these estimates as a result of changes in assumptions and actual investment returns , among other factors .cash flows used in investing activities the following table provides a summary of the major items affecting our cash flows used in investing activities: .
[['( in millions )', 'for the years ended december 31 , 2018', 'for the years ended december 31 , 2017', 'for the years ended december 31 , 2016'], ['net capital expenditures', '$ -1586 ( 1586 )', '$ -1434 ( 1434 )', '$ -1311 ( 1311 )'], ['acquisitions', '-398 ( 398 )', '-177 ( 177 )', '-204 ( 204 )'], ['other investing activities net ( a )', '-52 ( 52 )', '-61 ( 61 )', '-75 ( 75 )'], ['net cash flows used in investing activities', '$ -2036 ( 2036 )', '$ -1672 ( 1672 )', '$ -1590 ( 1590 )']]
( a ) includes removal costs from property , plant and equipment retirements and proceeds from sale of assets .in 2018 and 2017 , cash flows used in investing activities increased primarily due to an increase in our regulated capital expenditures , principally from incremental investments associated with the replacement and renewal of our transmission and distribution infrastructure in our regulated businesses , as well as acquisitions in both our regulated businesses and market-based businesses , as discussed below .our infrastructure investment plan consists of both infrastructure renewal programs , where we replace infrastructure , as needed , and major capital investment projects , where we construct new water and wastewater treatment and delivery facilities to meet new customer growth and water quality regulations .our projected capital expenditures and other investments are subject to periodic review and revision to reflect changes in economic conditions and other factors. .

Question: what are expected pension contributions in millions for 2020 and 2021?
Answer: 61