(a) The standard disability retirement annuity payable under this subtitle is the sum of a member's prior service annuity and current service annuity.
(b) A prior service annuity is subject to reduction as provided by Section 855.308(f).
(c) A standard disability retirement annuity is payable throughout the life of a retiree. When a retiree who receives an annuity under this section dies, an additional benefit may be payable under Section 854.502.