and carry such interest rate as the Board determines appropriate. (7) Bond guarantee The Board shall charge such fees for Bond guarantees made under this section as the Board determines appropriate. (8) Equity investments With respect to a QIP, the amount of an equity investment made by the AIF in such QIP may not exceed 20 percent of the total cost of the QIP. (9) Public-private partnership requirements At least 35 percent of the assistance provided under this section shall be provided to QIPs for which at least 10 percent of the financing for such QIPs comes from private debt or equity. (10) Prohibition on principal forgiveness With respect to a loan made under this section, the Board may not forgive any amount of principal on such loan. (d) American Infrastructure Bonds (1) In general Not later than 90 days after the date of the enactment of this Act, the Secretary, acting through the AIF, shall issue bonds, which shall be called American Infrastructure Bonds . The proceeds from the American Infrastructure Bonds shall be deposited into the AIF. (2) Forms and denominations