(a) An authority may at any time and from time to time sell and issue its refunding securities for the purpose of refunding the principal of and interest on any then outstanding securities of the authority, whether or not such securities shall have matured or be redeemable at the option of the authority at the time of such refunding, and for the payment of any expenses incurred in connection with such refunding and any premium or other sum necessary to be paid to redeem or retire the securities so to be refunded; provided however, that the principal amount of securities that the authority may at any time issue for refunding purposes shall not exceed the sum of the following:

(b) The principal proceeds derived by the authority from the sale of any refunding securities shall be used only for the payment of the principal of and the interest (and premium) on the securities being refunded and for payment of the expenses referred to in the preceding subdivision (4) of subsection (a) of this section; provided, that if in the judgment of the board such is necessary or desirable to effect an advantageous refunding, a portion of said proceeds may be used for payment of principal of and interest on such refunding securities themselves and the remainder of said proceeds for payment of the securities being refunded and of said expenses; and provided further, that any portion of said proceeds that shall at the time not be needed therefor, may be invested in such investments as are specified in Section 22-21-332.

(c) Any such refunding may be effected either by sale of refunding securities and the application of the proceeds thereof as provided in subsection (b) of this section, or by exchange of the refunding securities for the securities or coupons to be refunded thereby, or by any combination thereof; provided, that the holders of any securities or coupons so to be refunded shall not be compelled without their consent to surrender their securities or coupons for payment or exchange prior to the date on which they may be paid or redeemed by call of the authority under their respective provisions. All provisions of this article pertaining to securities of the authority that are not inconsistent with the provisions of this section shall, to the extent applicable, also apply to refunding securities issued by the authority and to securities issued by the authority for both refunding and other purposes.