(i) the dates during which the vice-chairman may exercise those powers and duties; and
(ii) that the powers and duties authorized to the vice-chairman shall not be exercised by the chairman during that designated time period. 7. In case of a vacancy in the office of chairman, the clerk of the board of supervisors shall call a meeting of the members of the board upon like notice as provided in subdivision one, at which a successor shall be selected chairman who shall be a member of the board. The person so selected shall serve as chairman of the board for the unexpired term of the previous chairman. In the event of the failure of the board to select such chairman within thirty days after the vacancy shall have occurred, the county clerk shall appoint a member of the board as chairman, who shall serve until the end of the calendar year in which he is appointed.