(a) Under such regulations and for such periods and at such prices as he may prescribe, the Secretary concerned or his designee may sell or contract to sell to purchasers within or in the immediate vicinity of an activity of the Army, Navy, Air Force, Marine Corps, or Coast Guard, as the case may be, any of the following utilities and related services, if it is determined that they are not available from another local source and that the sale is in the interest of national defense or in the public interest:

(b) Proceeds of sales under subsection (a) shall be credited to the appropriation currently available for the supply of that utility or service.

(c) To meet local needs the Secretary concerned may make minor expansions and extensions of any distributing system or facility within an activity through which a utility or service is furnished under subsection (a).