(1) Except as otherwise provided, any active contributing member of the retirement system who at one time had the state board of regents assist such member in the purchase of retirement annuities as provided in Kan. Stat. Ann. § 74-4925, and amendments thereto and who withdrew such member’s accumulated contributions upon the termination of such employment as provided in Kan. Stat. Ann. § 74-4925, and amendments thereto, may purchase such participating service credit for such service, and any active contributing member of the retirement system may purchase participating service credit for any waiting period required pursuant to Kan. Stat. Ann. § 74-4925, and amendments thereto, regardless of whether the state board of regents assisted such member in the purchase of retirement annuities as provided in Kan. Stat. Ann. § 74-4925, and amendments thereto. Such member may purchase, subject to the provisions of Kan. Stat. Ann. § 74-49,123, and amendments thereto, such service credit by submitting proof of such service acceptable to the board of trustees and electing in writing to have employee contributions deducted as provided in Kan. Stat. Ann. § 74-4919, and amendments thereto, from such member’s compensation at an additional rate of contribution, in addition to the employee’s rate of contribution as provided in Kan. Stat. Ann. § 74-4919, and amendments thereto, based upon the member’s attained age at the time of purchase and using actuarial assumptions and tables in use by the retirement system at such time of purchase for such periods of service. Such additional rate of contribution shall commence at the beginning of the quarter following such election and shall remain in effect until all of the full quarters of such service have been purchased.

(2) Any member of the Kansas public employees retirement system who has not retired may purchase, subject to the provisions of Kan. Stat. Ann. § 74-49,123, and amendments thereto, participating service credit for such service as described in this section with a participating employer by making a single lump-sum payment in lieu of employee contributions as provided in this section. The lump-sum payment shall be in an amount determined by the actuary using (a) the member’s then current annual rate of compensation or the member’s final average salary at the time the member elects to purchase such service credit, whichever is higher, (b) the actuarial assumptions and tables currently in use by the system and (c) the member’s attained age.