(a) This section applies only to members of:

(1) the Correctional Officers’ Retirement System;

(2) the Employees’ Retirement System; and

(3) the Teachers’ Retirement System.

(b) An ordinary disability retirement allowance equals the greater of:

(1) a normal service retirement allowance; or

(2) the amount computed under subsection (c) or (d) of this section.

(c) If a member is at least normal retirement age, the amount to be used under subsection (b)(2) of this section is 25% of the member’s average final compensation.

(d) If a member is under normal retirement age, the amount to be used under subsection (b)(2) of this section is the lesser of:

(1) 25% of the member’s average final compensation; or

(2) the normal service retirement allowance that is computed by using:

(i) the number of years of creditable service that the member would have received if the member continued employment until normal retirement age; and

(ii) an average final compensation that the member would have received if the member continued employment without a change in earnable compensation.