(a) All employees of state junior colleges and Athens State University who are participating in the Teachers' Retirement System of Alabama on July 22, 1987, may elect to purchase credit for their total years of service rendered to such employer prior to the time said employer was covered by the Teachers' Retirement System of Alabama, up to a maximum of five years.
(b) Any employee electing to purchase credit pursuant to subsection (a) shall pay to the Secretary-Treasurer within one year after October 1, 1987, a lump sum payment equal to a percentage of his or her then earnable compensation; the applicable percentage shall be the sum of the prevailing percentage rates of employer and member contributions as required by the actuarial valuations during the years for which such person is purchasing prior service credit.