(a) The law applicable to the Arkansas Teacher Retirement System shall be used to determine the annuity benefits to which an employee is entitled for service provided before or after Acts 1977, No. 793, if the employee:

1. (1) Was an employee of the Department of Human Services and became a member of the Arkansas Public Employees' Retirement System under the provisions of Acts 1977, No. 793, as amended; and
2. (2) Left employment with the department and became employed in a position covered by the Arkansas Teacher Retirement System.