The term “Federal benefit rate under subchapter XVI of this chapter” means, with respect to any month, the amount of the supplemental security income cash benefit (not including any State supplementary payment which is paid by the Commissioner of Social Security pursuant to an agreement under section
1382e
(a) of this title or section 212(b) of Public Law 93–66) payable under subchapter XVI of this chapter for the month to an eligible individual with no income.