During any month in which a member is assigned to the Ready Reserve of a uniformed service under conditions which meet the qualifications set forth in
section 1965(5)(B) of this title and is insured under a policy of insurance purchased by the Secretary under
section 1966 of this title, there shall be contributed from the appropriation made for active duty pay of the uniformed service concerned an amount determined by the Secretary (which shall be the same for all such members) as the share of the cost attributable to provided coverage under this section, less any costs traceable to the extra hazards of such duty in the uniformed services. Any amounts so contributed on behalf of any member shall be collected by the Secretary concerned from such member (by deduction from pay or otherwise) and shall be credited to the appropriation from which such contribution was made in advance on a monthly basis.