(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.