For the purpose of administering the system there is established a board of trustees, which shall be the members of the council of city of Okmulgee, Oklahoma, as now existing or as from time to time duly elected or appointed and constituted. The powers and duties of the board of trustees shall be as set forth in the system instrument attached to the ordinance codified in this article as exhibit A. (Ord. 1728 § 2, 1998)