The Authority is hereby authorized by resolution to provide for the issuance of refunding revenue bonds with which to refund outstanding revenue bonds or any issue or series of such outstanding bonds, which refunding revenue bonds may be issued at or before the maturity or redemption date of the bonds to be refunded, and to include different issues or series of such outstanding revenue bonds by a single issue of refunding revenue bonds, and to issue refunding revenue bonds to pay any redemption premium and interest to accrue and become payable on the outstanding revenue bonds being refunded to the date of payment or redemption, and to establish reserves for such refunding revenue bonds. Such refunding revenue bonds shall be payable solely from all or that portion of the revenues of the Authority facilities pledged to the payment thereof in the bond resolution pursuant to which such bonds were issued. Such refunding revenue bonds may, in the discretion of the Authority, be exchanged at par for the revenue bonds that are being refunded or may be sold at public or private sale in such manner and at such price as the Authority shall deem for the best interests of the Authority, but no such sale shall be made at a price so low as to require the payment of interest on the money received therefor at more than six percent per year, computed with relation to the absolute maturity of the bonds in accordance with standard tables of bond values, excluding from such computation the amount of any premium to be paid on the redemption of any bonds prior to maturity, and may be issued and delivered at any time prior to the date of redemption or maturity date of the bonds to be refunded as the Authority determines to be in the best interests of the Authority. The interest rate or rates on refunding revenue bonds shall not be limited by the interest rate or rates borne by any of the revenue bonds to be refunded thereby. The proceeds derived from the sale of refunding revenue bonds issued under this chapter shall be invested in obligations of or guaranteed by the United States government pending the application of such proceeds to the purpose for which such refunding revenue bonds have been issued. To further secure such refunding revenue bonds, the Authority may contract with the purchasers thereof with respect to the safekeeping and application of the proceeds thereof and the safekeeping and application of the earnings of such investments. The determination of the Authority with respect to the financial soundness and advantage of the issuance and delivery of refunding revenue bonds authorized under this chapter shall be conclusive, but nothing contained in this section shall require the holders of any outstanding revenue bonds being refunded to accept payment thereof otherwise than as provided in the outstanding bonds.