Sec. 18. The proceeds of any bonds issued for the purpose of refunding outstanding bonds may, in the discretion of the authority:
(1) be applied to the purchase or retirement at maturity or redemption of the outstanding bonds either on their earliest or any subsequent redemption date or upon the purchase or at the maturity of the outstanding bonds; and
(2) pending the application of the proceeds, be placed in escrow to be applied to the purchase or retirement at maturity or redemption of the outstanding bonds on a date determined by the authority.