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.