; (iii) in the case of a single-employer plan for any plan year beginning in a fiscal year with respect to which the average of the single-employer pension insurance program funded percentages for the 2 fiscal years immediately preceding such fiscal year is at least 90 percent but less than 100 percent, an amount for each individual who is a participant in such plan during the plan year equal to the sum of $64 and an additional premium equal to the quotient (not to exceed $500) obtained by dividing— (I) an amount equal to $28 for each $1,000 (or fraction thereof) of unfunded vested benefits under the plan as of the close of the preceding plan year, by (II) the number of participants in such plan as of the close of the preceding plan year; (iv) notwithstanding clauses (i) through (iii), in the case of a CSEC plan (as defined in section 210(f)) or single-employer plan maintained by a small employer for any plan year, an amount for each individual who is a participant in such plan during the plan year equal to the sum of $19 and an additional premium equal to the quotient (not to exceed $500) obtained by dividing— (I) an amount equal to $9 for each $1,000 (or fraction thereof) of unfunded vested benefits under the plan as of the close of the preceding plan year, by (II) the number of participants in such plan as of the close of the preceding plan year