(a) Within thirty (30) days after their appointment, the commissioners shall take and file their oath of office with the county clerk. In their oath they shall swear that they will support the Constitution of the United States and the Constitution of the State of Arkansas, that they will discharge faithfully their duties as commissioners, and that they will not be interested, directly or indirectly, in any contract let by the board.
(b) Any commissioner failing to file such oath within the thirty-day period shall be deemed to have declined the office, and the county court shall appoint some property holder as his successor, who shall qualify in like manner within a like time.