; (iii) an applicant for supplemental security income benefits under title XVI; (iv) an individual who is needed in the home of the individual to care for a disabled member of the family of the individual; or (v) an individual who (but for the exercise of the State option under this clause) would be a work-eligible individual under a tribal family assistance plan approved under section 412 or under a tribal work program to which funds are provided under this part. (b) Calculation of participation rates (1) Average monthly rate For purposes of subsection (a), the participation rate of a State for a fiscal year is the average of the participation rates of the State for each month in the fiscal year. (2) Monthly participation rate For purposes of paragraph (1), the participation rate of a State for a month, expressed as a percentage, is— (A) the number of families residing in the State that include a work-eligible individual who is engaged in work for the month