Any member of the Kansas public employees retirement system who was previously employed in service as law enforcement personnel in support of a mission administered by the united nations, may purchase participating service credit for periods of such service which commenced on or after January 1, 1962. Such purchase of participating service credit shall be made in accordance with the provisions of Kan. Stat. Ann. § 74-49,123, and amendments thereto. The benefit for each such period of service purchased by the member shall be equal to 1.75% of the final average salary of any such member. Such member may purchase such participating service credit by submitting proof of such service acceptable to the board of trustees and by making application therefor prior to the date of retirement of such member for such purchase and to have such member’s employee contributions deducted 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 the date upon which such member made application for such purchase and shall remain in effect until all of the full quarters of such service have been purchased. In lieu of the deduction of employee contributions as provided in this section, any such member may purchase such participating service credit by means of a single lump-sum payment in an amount equal to the then present value of benefits being purchased as determined by the actuary using the member’s attained age at the time of purchase, annual compensation at the time of purchase and the actuarial assumptions and tables currently in use by the system. The lump-sum payment shall be made immediately upon being notified of the amount due under this purchase method. The provisions of this section shall be part of and supplemental to the provisions of Kan. Stat. Ann. § 74-4901 et seq., and amendments thereto.