“Gain and Loss Reserve” means a segregated account within the retirement fund that is established and maintained to do either of the following:
(a) Credit interest to members’ Defined Benefit Supplement accounts at the minimum interest rate for plan years in which the board determines that the obligation cannot be met from the plan’s investment earnings with respect to the Defined Benefit Supplement Program.
(b) Provide additions to the Annuitant Reserve to meet the plan’s obligation for annuities payable under the Defined Benefit Supplement Program.