(v)
as determined by the agency under regulations prescribed by the Office, is within the scope of the offer of voluntary early retirement, which may be made on the basis of—
(I)
1 or more organizational units;
(II)
1 or more occupational series or levels;
(III)
1 or more geographical locations;
(V)
skills, knowledge, or other factors related to a position; or
(VI)
any appropriate combination of such factors.
after completing 25 years of service, or after becoming 50 years of age and completing 20 years of service, is entitled to an annuity.