(a) Multiyear Contracts Authorized.—
(b) Limitations on Contracts for Periods in Excess of Five Years.—The Secretary may exercise the authority in subsection (a) to enter into a contract for a period in excess of five years only if the Secretary determines, on the basis of a business case analysis prepared by the Department of Defense, that—
the proposed purchase of electricity under such contract is cost effective for the Department of Defense; and
(c) Relationship to Other Multiyear Contracting Authority.—
Nothing in this section shall be construed to preclude the Department of Defense from using other multiyear contracting authority of the Department to purchase renewable energy.