(1) When a member employed on a part-time basis is eligible to purchase periods of full-time service, the compensation used to calculate the cost to purchase such full-time service will be the actual part-time compensation earned.

(2) If the member later retires with a full-time FAS, the full-time service purchased under (1) will be proportionally reduced based upon the proportion of time worked when the service was purchased.

(3) A member whose service is reduced under (2) above may elect to purchase service to equal full-time by paying the difference between the cost actually paid and the cost had the member's salary been full-time, plus interest.