4.__Members qualified for credit at subsidized cost.__A member qualified under subsection 3 to purchase service credit at the cost set forth in this subsection is entitled to service credit upon payment of back contributions under section 17713, subsection 2.__Upon complete payment of back contributions, the member must be granted service credit for the period of time for which payment is made.__Upon making partial payment, the member must be granted service credit on a pro rata basis in accordance with rules adopted by the board.

5.__Members qualified for credit at actuarial cost.__A member qualified under subsection 3 to purchase service credit at the cost set forth in this subsection is entitled to service credit if the member pays into the Members' Contribution Fund an amount that, together with regular interest on that amount, is the actuarial equivalent, at the effective date of the retirement benefit, of the portion of the retirement benefit based on the additional creditable service.

A.__Payment must be made before any retirement benefit becomes effective for that member.

B.__Payment may be made to the retirement system by a single direct payment or by annual direct payments in accordance with section 17701, subsection 4.

C.__A person who purchases service credit under this subsection and who subsequently, without inclusion of the purchased service credit and prior to retirement, becomes qualified for service credit at the cost set forth in subsection 4 is entitled to purchase the service credit under section 17713, subsection 2 and to receive a refund of the amount paid under this subsection that exceeds the cost to purchase the service credit under section 17713.__A person who would have been qualified to purchase service credit under subsection 4 prior to retirement if a timely appropriation had been made under subsection 6 is entitled to a refund under this subsection even if the person becomes qualified after retirement.

6.__Cost subsidy for certain award recipients; annual report.__ A recipient of an award described in subsection 3, paragraph A, subparagraph (3) may purchase service credit at a subsidized cost under subsection 4 only if the retirement system has received an appropriation of the difference between the