; (C) to the extent the average total allowed charges per year per individual that uses such drug or biological are less than $100; or (D) that is a vaccine described in subparagraph (A) or (B) of section 1861(s)(10). (4) Rebate amount (A) In general For purposes of paragraph (2)(B)(i), the amount specified in this paragraph for a rebatable drug assigned to a billing and payment code for a rebate period is, subject to paragraph (5), the amount equal to the product of— (i) the total number of units for which payment was made under this part for such rebatable drug during the rebate period; and (ii) the amount (if any) by which— (I) the applicable manufacturer’s average sales price (as determined under subparagraph (B)) for such rebatable drug for sales that occurred two quarters prior to the rebate period; exceeds (II) the inflation-adjusted ASP determined under subparagraph (C) for such rebatable drug for sales that occurred two quarters prior to the rebate period. (B) Determination of applicable manufacturer’s ASP The applicable manufacturer’s average sales price, with respect to a manufacturer, determined under this subparagraph for a billing and payment code is the weighted average of the average sales prices of all of the rebatable drugs of the manufacturer identified by a national drug code assigned to such billing and payment code for sales that occurred two quarters prior to the rebate period. (C) Determination of inflation-adjusted ASP The inflation-adjusted ASP determined under this subparagraph for a rebatable drug for a rebate period is— (i) the average sales price for the billing and payment code for all units of such drug for sales that occurred in the ASP benchmark quarter (as defined in subparagraph (E))