For purposes of retirement and survivor annuities, in the case of a member who first became a member of the System prior to January 1, 1998 and who is eligible to receive an alternative retirement annuity under Section 14-110 of the Code on or after that date, "final average compensation" means final average compensation as defined by Section 14-103.12(a), (c) or (d) of the Code, whichever is greater.
Ill. Admin. Code tit. 80, § 1540.410