(1)
Not less often than every four years, the Secretary of Defense shall carry out an actuarial valuation of the Fund. Each such actuarial valuation shall include—
(A)
a determination (using the aggregate entry-age normal cost method) of a single level dollar amount for members of the participating uniformed services on active duty and full-time National Guard duty, but excluding any member who would be excluded for active-duty end strength purposes by section
115
(i) of this title; and
(B)
a determination (using the aggregate entry-age normal cost method) of a single level dollar amount for members of the Selected Reserve of the participating uniformed services who are not otherwise described by subparagraph (A).
Such single level dollar amounts shall be used for the purposes of subsection (b). The Secretary of Defense may determine a separate single level dollar amount under subparagraph (A) or (B) for any participating uniformed service, if, in the judgment of the Secretary, such a determination would produce a more accurate and appropriate actuarial valuation for that uniformed service.