Subject to agreements with bondholders that may then exist, the authority may purchase out of funds available for the purpose, bonds of the authority which shall then be canceled, at a price not exceeding the following amounts:
(1) if the bonds are then redeemable, the redemption price then applicable plus accrued interest to the next interest payment date of the bonds; or
(2) if the bonds are not redeemable, the redemption price applicable on the first date after the purchase upon which the bonds become subject to redemption plus accrued interest to that date.