(a) The bonds shall be payable as provided by the board and shall mature serially or otherwise not later than 40 years from their date.
(b) Bonds previously issued shall mature according to their provisions.
(c) The board shall determine the medium of payment for both principal of and interest on the bonds.
(d) The board at its own option may make the bonds redeemable or subject to tender for purchase before maturity at the price and under the terms and conditions fixed by the board in the resolution providing for the issuance and sale of the bonds.