(1) Pledges to the payment of any bond issue requirements, sinking or reserve funds, as may be provided for under the terms of this article;
(2) Payment of any outstanding unpaid bond obligations or administrative expenses;
(3) The construction of any project requested by the board, the cost of which may amount to a sum less than the accumulated balance of such fund;
(4) The most advantageous obtainable purchase redemption and retirement of the authority's bonds pursuant to privileges accorded to the authority in the various issues of bonds outstanding;
(5) The most advantageous open market purchase of the authority's bonds that it may accomplish; or
(6) Investment in obligations of the United States government or obligations of agencies of the United States government, the payment of which is guaranteed by the United States government, of guaranteed convertibility or maturity not in excess of two years, provided that funds so invested and income from such investments shall always be available to and ultimately expended for other purposes set forth in this Code section.