Pursuant to Sec. 2.21(a), subject to reservations in Sec. 2.21(b), and subject to policy guidance and direction by the Under Secretary, the following delegation of authority is made by the Under Secretary for Research, Education, and Economics, to be exercised only during the absence or unavailability of the Under Secretary: Perform all the duties and exercise all the powers which are now or which may hereafter be delegated to the Under Secretary for Research, Education, and Economics.