The heads of Federal agencies must—

(a) Cooperate with and assist the Administrator of General Services in carrying out his responsibilities respecting office buildings and space;

(b) Take measures to give GSA early notice of new or changing space requirements;

(c) Seek to economize their requirements for space; and

(d) Continuously review their needs for space in and near the District of Columbia, taking into account the feasibility of decentralizing services or activities that can be carried on elsewhere without excessive costs or significant loss of efficiency.