(a) Persons entitled to receive allowances under the plan under this part may authorize deductions to be made from those allowances, in accordance with procedures established by the board.
(b) The board shall determine the additional cost involved in making deductions under this section, and may require the public agency, association, insurance carrier, or unit thereof to pay the amount of the additional cost to the board for deposit in the retirement fund to the credit of the Defined Benefit Program.