Notwithstanding the provisions of Kan. Stat. Ann. §§ 74-4902 and 74-4913 to the contrary, an employee who became a member of the Kansas public employees retirement system on January 1, 1962, who was first employed by a participating employer on March 1, 1938, and terminated employment on August 31, 1962, and who subsequently became a member of the Kansas school retirement system on September 1, 1962, until January 1, 1971, when the Kansas school retirement system was merged into the Kansas public employees retirement system. Upon retirement the prior service credit of both systems shall be combined and a prior service benefit shall be computed by using a prior service annual salary of seven thousand eight hundred forty-four dollars ($7,844).