(a) Each member shall contribute $4.00 monthly as the employee contribution toward the cost of the retirement system. Each local unit of administration shall deduct such amount each month from the compensation of each of its employees who is a member of the retirement system and pay the amounts so deducted to the board. The board shall specify by rules and regulations the time and manner such amounts shall be paid to it.

(b) The employer contributions toward the cost of the retirement system shall be as actuarially determined and approved by the board; and, in making such determination, each local unit of administration shall supply the board with such information at such times and in such manner as the board shall specify by rules and regulations. The amounts determined as the employer contributions shall be certified to the director of the Office of Treasury and Fiscal Services at such times as the board shall specify by rules and regulations. It shall be the duty of the director of the Office of Treasury and Fiscal Services to pay to the board, from funds appropriated or otherwise available to the retirement system, the amounts so certified by the board. All employer contributions shall be irrevocable and may be used only for the exclusive benefit of members or their beneficiaries.