((a)) ** Authorization of Administrator; contents of contracts** Subject to the provisions of this chapter and to such rate schedules as the Secretary of Energy may approve, as provided in this chapter, the administrator shall negotiate and enter into contracts for the sale at wholesale of electric energy, either for resale or direct consumption, to public bodies and cooperatives and to private agencies and persons and for the disposition of electric energy to Federal agencies. Contracts for the sale of electric energy to any private person or agency other than a privately owned public utility engaged in selling electric energy to the general public, shall contain a provision forbidding such private purchaser to resell any of such electric energy so purchased to any private utility or agency engaged in the sale of electric energy to the general public, and requiring the immediate canceling of such contract of sale in the event of violation of such provision. Contracts entered into under this subsection shall be binding in accordance with the terms thereof and shall be effective for such period or periods, including renewals or extensions, as may be provided therein, not exceeding in the aggregate twenty years from the respective dates of the making of such contracts. Contracts entered into under this subsection shall contain (1) such provisions as the administrator and purchaser agree upon for the equitable adjustment of rates at appropriate intervals, not less frequently than once in every five years, and (2) in the case of a contract with any purchaser engaged in the business of selling electric energy to the general public, the contract shall provide that the administrator may cancel such contract upon five years’ notice in writing if in the judgment of the administrator any part of the electric energy purchased under such contract is likely to be needed to satisfy the requirements of the said public bodies or cooperatives referred to in this chapter, and that such cancelation may be with respect to all or any part of the electric energy so purchased under said contract to the end that the preferential rights and priorities accorded public bodies and cooperatives under this chapter shall at all times be preserved. Contracts entered into with any utility engaged in the sale of electric energy to the general public shall contain such terms and conditions, including among other things stipulations concerning resale and resale rates by any such utility, as the administrator may deem necessary, desirable or appropriate to effectuate the purposes of this chapter and to insure that resale by such utility to the ultimate consumer shall be at rates which are reasonable and nondiscriminatory. Such contracts shall also require such utility to keep on file in the office of the administrator a schedule of all its rates and charges to the public for electric energy and such alterations and changes therein as may be put into effect by such utility.

((b)) ** Exchange of excess power** The administrator is authorized to enter into contracts with public or private power systems for the mutual exchange of unused excess power upon suitable exchange terms for the purpose of economical operation or of providing emergency or break-down relief.