For each member of the plan, an employer shall contribute to the teachers’ and public employees’ retiree health reimbursement arrangement plan trust fund an amount equal to three percent of the average annual compensation of all employees of all employers in the teachers’ retirement system and public employees’ retirement system. The administrator shall maintain a record for each member to account for employer contributions on behalf of that member. The board shall establish by regulation the rate of interest to be applied annually to the amount in a member’s individual account.