The Authority is hereby authorized to provide, by resolution of the board, for the issuance of refunding bonds for the purpose of refunding any bonds of the Authority issued under the provisions of this act and then outstanding, either by voluntary exchange with the holders of such outstanding bonds or to provide funds to redeem and retire such outstanding bonds, with accrued interest, and any premium payable thereon at maturity or at any call date. The issuance of such refunding bonds, the maturities and other details thereof, the rights of the holders thereof, and the duties of the Authority in respect to the same, shall be governed by the foregoing provisions of this act in so far as the same may be applicable. Refunding bonds may be issued by the Authority to refund bonds originally issued or to refund bonds of the Authority previously issued for refunding purposes. Notwithstanding the provisions of section 6(a) of this act,¹ refunding bonds for bond issues closed by the Authority during calendar year 1975 may be sold at private sale, without advertisement or competitive bidding, for such price or prices as the Authority shall determine.