The Montgomery County Board shall provide from the Montgomery County Public Schools Employees’ Pension System Trust the supplemental retirement allowance required under subsection (b) of this section. The Montgomery County Board, through the Montgomery County Public Schools Employees’ Pension System Trust, shall pay a supplemental retirement allowance to an employee of the county board who retires on or after July 1, 1999, as a member of the Teachers’ Pension System of the State of Maryland. The supplemental retirement allowance shall equal the product of the member’s years of creditable service earned in the Montgomery County Public Schools Employees’ Pension System times the sum of: 08% of the retiree’s average final compensation that does not exceed the Social Security integration level; and 15% of the retiree’s average final compensation that exceeds the Social Security integration level.