; and (B) $80,000. (c) Investment of amounts (1) In general The Secretary of the Treasury shall invest the portion of the Fund that is not, in the judgment of the Secretary of the Treasury, required to meet current withdrawals. (2) Requirement Investments under paragraph (1) may be made only in interest-bearing obligations of the United States. (3) Acquisition of obligations For the purpose of investments under paragraph (1), obligations of the United States may be acquired— (A) on original issue at the issue price; or (B) by purchase of outstanding obligations at market price. (4) Sale of obligations Any obligation of the United States acquired by the Fund may be sold by the Secretary of the Treasury at market price. (5) Credits to fund The interest on, and the proceeds from the sale or redemption of, any obligations held in the Fund shall be credited to and form a part of the Fund. (d) Transfers of amounts (1) In general Not less frequently than monthly, the Secretary of the Treasury shall transfer from the general fund of the Treasury to the Fund the amounts required to be transferred to the Fund under this section on the basis of estimates made by the Secretary of the Treasury. (2) Adjustments In carrying out paragraph (1), the Secretary of the Treasury shall make proper adjustments in amounts transferred to the Fund to the extent that prior estimates were in excess of or less than the amounts required to be transferred under this section. (e) Acceptance and use of donations (1) In general The Secretary may accept for the Government, and shall transfer to the Secretary of the Treasury for deposit into the Fund, a gift to provide assistance under section 104 of— (A) money; (B) an obligation of the Government included in the public debt made only on the condition that the obligation be canceled and retired and not reissued