Sec. 18. (a) The bonds, notes, or other evidences of indebtedness shall be executed in the name of the district by the chairman of the board and attested by the secretary. Interest coupons may be executed by placing the facsimile signature of the chairman on the coupons.
(b) The bonds, notes, or other evidences of indebtedness are valid and binding obligations of the district for all purposes provided by this chapter and in the resolution, even if before delivery any of the persons whose signatures appear on the bonds, notes, or other evidences of indebtedness have ceased to be officers of the district.