(a) A member who established during December, 1977, service credit for administrative board service performed during that month, may:
(1) remain a contributing member of the retirement system accruing service credit in the employee class for continuous service on an eligible board; and
(2) establish service credit for previous service on an eligible board.
(b) Contributions for administrative board service are computed on the basis of the highest salary paid during the time for which credit is sought to an officer or employee of the agency, commission, or department on whose board the member serves.