; and (B) between payments included under subsection (a)(1) and payments described in subsection (a)(4). (4) Transition to a corridor around the national average (A) Determination of national average base per beneficiary, per category amount Subject to subparagraph (C), the Secretary shall determine a national average base per beneficiary, per category amount equal to the average of the base per beneficiary, per category amounts for each of the 50 States and the District of Columbia determined under paragraph (2) , weighted by the average number of beneficiaries in each such category and State as determined by the Secretary consistent with subsection (d) for the base fiscal year. (B) Transition adjustment (i) High per beneficiary states In the case of a high per beneficiary State (as defined in clause (iii)(I) ) for a category, the beneficiary-based quarterly amount for such State and category for a quarter in a reform year (beginning with the fourth reform year and ending with the tenth reform year) is equal to the sum of— (I) the product of the State-specific factor for such reform year (as defined in clause (iv) ) and the beneficiary-based quarterly amount that would otherwise be determined under paragraph (1) for such State and category if the State were a State described in clause (ii) of paragraph (1)(C), instead of a State described in clause (i) of such paragraph