A member of the county board of commissioners shall not be interested directly or indirectly in any contract or other business transaction with the county, or a board, office, or commission thereof, during the time for which he is elected or appointed, nor for one year thereafter unless the contract or transaction has been approved by 3/4 of the members of the county board of commissioners and so shown on the minutes of the board together with a showing that the board is cognizant of the member’s interest. This prohibition is not intended to apply to appointments or employment by the county, or its officers, boards, committees, or other authority, which appointments and employment shall be governed by the provisions of section 30a of this act.