The board is hereby authorized to contract with the owners of the buildings so erected upon said leased grounds to pay as rental or otherwise for the use of said buildings a sum sufficient to pay, on the amortization plan, the principal and interest thereon of the cost of construction and equipment of said buildings, such contracts to run not over forty years. The amount of the cost of construction and equipment used in any such contract shall not exceed the estimated cost of construction and equipment which shall be made by the secretary of administration. The rate of interest allowed on the cost of construction and equipment shall not exceed six percent per annum, payable annually or semiannually as may be determined by the board. Said contract shall provide:
K.S.A. 76-6a03