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