In accordance with rules adopted by the board, a former member who is entitled to a deferred allowance pursuant to section 70.675 may elect for the system to pay the reserve value of the deferred allowance if the amount of the former member’s credited service is less than ten years and if the former member is not within ten years of his or her minimum service retirement age at the time of payment of the reserve value. The reserve value shall be the actuarial equivalent of the allowance otherwise payable. Any lump sum payment so made shall be a complete discharge of all liability under the system with respect to such allowance.