(2) Each employee who elects to be assisted under subsection (1) of this section shall, as a condition to such election, either:
(a) Agree to contribute through payroll deductions toward the purchase of the supplementary retirement benefits a percentage of the annual salary of the employee in excess of $4,800 equal to the percentage rate applicable to contributions made by the employee under the system, the amounts deducted from payrolls as employee contributions to be paid promptly by the board to the life insurance or annuity company in accordance with the terms of the applicable contract; or
(b) Agree either to a reduction in salary or to the forgoing of a salary increase in accordance with ORS 243.820, in an amount not less than the amount otherwise required to be contributed under paragraph (a) of this subsection. [1965 c.297 §2(1), (2); 1969 c.626 §1]