(1) If employment is not terminated at the end of the period specified for participation, the plan participant shall resume active contributing membership in the system, and upon termination of employment, he shall receive an additional retirement benefit based on his additional service rendered since termination of participation in the fund, using the normal method of computation of benefit, subject to the following:
(a) If his period of additional service is less than thirty-six months, the average compensation figure used to calculate the additional benefit shall be that used to calculate his original benefit.(b) If his period of additional service is thirty-six or more months, the average compensation figure used to calculate the additional benefit shall be based on his compensation during the period of additional service.(c) The optional allowance applied to the additional retirement benefit shall be the same optional allowance selected in accordance with R.S. 11:2259 for the original benefit.(d) In no event shall the additional benefit exceed an amount which, when combined with the original benefit, equals one hundred percent of the average compensation figure used to compute the additional benefit.