Subject to subsection (b) of this section, nothing in this chapter shall affect the authority of any management official of any agency
(2) in accordance with applicable laws
(A) to hire, assign, direct, layoff, and retain employees in the agency, or to suspend, remove, reduce in grade or pay, or take other disciplinary action against such employees;
(B) to assign work, to make determinations with respect to contracting out, and to determine the personnel by which agency operations shall be conducted;
(C) with respect to filling positions, to make selections for appointments from
(i) among properly ranked and certified candidates for promotion; or
(ii) any other appropriate source; and
(D) to take whatever actions may be necessary to carry out the agency mission during emergencies.