The amount of the employee's benefit after reduction for any deficiency under §847.608 is—

(a) For CSRS, the maximum amount that may be designated as the survivor base under section 8339 (j) or (k) to title 5, United States Code;

(b) For FERS, the employee annuity (for survivor benefit purposes) under sections 8416 through 8420 of title 5, United States Code.