(1) The bonds shall be executed by the manual or facsimile signatures of the chairman and secretary of the authority.
(2) In case any of the officers whose signatures appear on the bonds or coupons shall cease to be such officers before the delivery of the bonds or coupons, their signatures shall nevertheless be valid and sufficient for all purposes.
(3) The coupons attached to the bonds may be executed by the facsimile signature of the chairman of the authority.