A nonmember shall be retired upon his or her written application to the board if all of the following conditions are met:

1. (a) The nonmember has attained the age of 50.
2. (b) On the date the parties separated, the member had at least five years’ credited service, as defined by Section 75004.
3. (c) On the date of application of the nonmember, the member is eligible to retire and receive an allowance as provided in Section 75025, 75032, 75033, or 75033.5.