(a) An alternate for a member of the Board shall act in the place and stead of such member in his or her absence or in the event of his or her death, removal, resignation, or disqualification, until a successor for his or her unexpired term has been selected and has qualified.

(b) In the event any member of the Board and his or her alternate are both unable to attend a meeting of the Board, any alternate for any other member representing the same group as the absent member may serve in the place of the absent member, or in the event such other alternate cannot attend, or there is no such other alternate, such member, or in the event of his disability or a vacancy, his or her alternate may designate, subject to the disapproval of the Secretary, a temporary substitute to attend such meeting. At such meeting such temporary substitute may act in the place of such member.