The heat and power plant of the University of Nebraska, together with tunnels and conduits appurtenant thereto, shall be operated and maintained under the immediate control of the Board of Regents of the University of Nebraska. Such plant shall supply heat, light, and power for use at the University of Nebraska, the State Capitol, including the executive mansion, and the Nebraska State Historical Society. At the sole discretion of the Director of Administrative Services, in consultation with the Board of Regents, alternative sources of heat, power, and light may be utilized, and in such event, adequate notice of any change shall be given to the Board of Regents. Cost of operation and maintenance of the plant and its appurtenances shall in the first instance be borne by the Board of Regents. The cost of operation, repairs, and maintenance shall be apportioned between the University of Nebraska, the State Capitol, including the executive mansion, and the Nebraska State Historical Society, upon the percentage of heat, light, and power received by each. At the end of each month, the Board of Regents shall forward to the administrator a bill for the share of the cost of operation for such month chargeable to the State Capitol, including the executive mansion, and to the Director of the Nebraska State Historical Society for the share of the cost of operation for such month chargeable to the Nebraska State Historical Society. The Board of Regents shall forward annually to the administrator a statement for the share of the cost of repairs and maintenance chargeable to the State Capitol, including the executive mansion, and to the Director of the Nebraska State Historical Society for the share of the cost of repairs and maintenance chargeable to the Nebraska State Historical Society. If no objection in writing is made by the administrator or the Director of the Nebraska State Historical Society within ten days after the receipt of such statements, they shall constitute valid obligations to be paid in the manner prescribed by law for payment of operating expenses of the State Capitol and by the Nebraska State Historical Society from funds appropriated for that purpose by the Legislature. In case objection shall be made, the Board of Regents and the administrator or the Director of the Nebraska State Historical Society, whichever shall object, shall endeavor to arrive at a proper charge and, in case of inability to do so, shall submit the matter to arbitration, one arbitrator to be named by each party and the third to be chosen by those so named. The amount fixed by the arbitrators shall constitute a valid obligation to be paid in the manner indicated above.