(a) Under regulations prescribed by the Secretary of Defense, each officer required under section 1181 of this title to show cause for retention on active duty—
(1)
shall be notified in writing, at least 30 days before the hearing of his case by a board of inquiry, of the reasons for which he is being required to show cause for retention on active duty;
(2)
shall be allowed a reasonable time, as determined by the board of inquiry, to prepare his showing of cause for his retention on active duty;