and the applicable percentage subsidy assigned under the program shall be based on the ability of each project to meet the criteria established under section 8(d). (4) Limitations (A) Per bond subsidy The applicable percentage with respect to any bond may not exceed 40 percent. (B) Aggregate subsidy limitation For any calendar year, the aggregate amount of interest subsidies provided under this section with respect to all American Infrastructure Bonds shall not exceed an amount equal to 28 percent of interest payable under all such bonds. 18. National Infrastructure Development Bank Trust Fund (a) In general There is established in the Treasury of the United States a trust fund to be known as the National Infrastructure Development Bank Trust Fund consisting of such amounts as may be appropriated to such trust fund as provided in this section. (b) Transfer to trust fund There are hereby appropriated to the National Infrastructure Development Bank Trust Fund such amount as the Secretary of the Treasury estimates is equivalent to the tax receipts attributable to interest payable under American Infrastructure Bonds. (c) Expenditures from trust fund Amounts in the National Infrastructure Development Bank Trust Fund shall be available, as provided in appropriation Acts, only for purposes of the Secretary making transfers to the National Infrastructure Development Bank for infrastructure project assistance provided by the Bank under this Act. 19. Authorization of appropriations There is authorized to be appropriated $5,000,000,000 for each of fiscal years 2017, 2018, 2019, 2020, and 2021 to capitalize the Bank and to remain available until expended, of which not more than $25,000,000 for each of fiscal years 2017 and 2018, and not more than $50,000,000 for each fiscal year thereafter, may be used for administrative costs of the Bank.