The board, subject to existing agreements with noteholders or bondholders, may, out of any funds available for that reason, purchase notes or bonds of the board, which shall thereupon be canceled, at a price not exceeding:
(1) the current redemption price plus accrued interest to the next interest payment thereon, if the notes or bonds are then redeemable; or
(2) the redemption price applicable on the first date after the purchase upon which the notes or bonds become subject to redemption plus accrued interest to that date, if the notes or bonds are not then redeemable.