(a) A member claiming credit in the employee class for membership service not previously established shall, for each month of the service, pay a contribution in an amount equal to the greater of:
(1) the appropriate member contribution provided by Section 815.402 for the service during the time for which credit is sought; or
(2) $18.
(b) A member claiming credit in the employee class for military service not previously established shall, for each month of the service, pay a contribution in an amount equal to the greater of:
(1) the amount that the member contributed for the first full month of membership service that is after the member's date of release from active military duty and that is credited in the retirement system; or
(2) $18.