It shall be the duty of the Secretary of the Treasury to invest, at the direction of the Foundation Board, in full the amounts appropriated to the Trust Fund. Such investments shall be in public debt securities with maturities suitable to the needs of the Trust Fund. Investments in public debt securities shall bear interest “at rates determined by the Secretary of the Treasury taking into consideration the current average market yield on outstanding marketable obligations of the United States” of comparable maturity. Beginning on October 1, 2023, and thereafter, interest earned from investments made with any new appropriations to the Trust Fund shall only be available subject to appropriations and is authorized to be appropriated to carry out the provisions of this chapter.