Any accrued interest received upon delivery of bonds or notes of an interstate district shall be applied to the payment of the first interest which becomes due thereon. The other proceeds of the sale of such bonds or notes, other than temporary notes, including any premiums, may be temporarily invested by the interstate district pending their expenditure; and such proceeds, including any income derived from the temporary investment of such proceeds, shall be used to pay the costs of issuing and marketing the bonds or notes and to meet the operating expenses or capital expenses in accordance with the purposes for which the bonds or notes were issued or, by proceedings taken in the manner required for the authorization of such debt, for other purposes for which such debt could be incurred. No purchaser of any bonds or notes of an interstate district shall be responsible in any way to see to the application of the proceeds thereof.   [PL 1981, c. 693, §§ 5, 8 (NEW).]