Pursuant to § 2.17(a), subject to reservations in § 2.17(b), and subject to policy guidance and direction by the Under Secretary for Rural Development, the following delegation of authority is made to the Deputy Under Secretary for Rural Development, 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 Rural Development.