((a)) ** .—** The Secretary of the Navy may by regulation implement by requiring that the promotion zone for consideration of officers on the reserve active-status list of the Navy or the Marine Corps for promotion to the next higher grade be determined in accordance with a running mate system as provided in subsection (b).

((b)) ** .—** An officer to whom a running mate system applies shall be assigned as a running mate an officer of the same grade on the active-duty list of the same armed force. The officer on the reserve active-status list is in the promotion zone and is eligible for consideration for promotion to the next higher grade by a selection board convened under when that officer’s running mate is in or above the promotion zone established for that officer’s grade under chapter 36 of this title.

((c)) ** .—** If the Secretary of the Navy authorizes the selection of officers for promotion from below the promotion zone in accordance with , the number of officers to be considered from below the zone may be established through the application of the running mate system or otherwise as the Secretary determines to be appropriate to meet the needs of the Navy or Marine Corps.