; or (ii) an amount equal to a percentage of, to be determined by the Secretary, but not to exceed 3 percent of, adjusted gross receipts calculated under subparagraph (F). (F) Adjusted gross receipts For the purposes of subparagraphs (D)(ii) and (E)(ii), the Secretary shall calculate the adjusted gross receipts collected for each trip or event authorized under a special recreation permit, using either of the following calculations, based on the election of the recreation service provider: (i) The sum of— (I) the product obtained by multiplying— (aa) the general amount paid by participants of the trip or event to the recreation service provider for the applicable trip or event (excluding amounts related to goods, souvenirs, merchandise, gear, and additional food provided or sold by the recreation service provider); and (bb) the quotient obtained by dividing— (AA) the number of days of the trip or event that occurred on Federal recreational lands and waters covered by the special recreation permit, rounded to the nearest whole day; by (BB) the total number of days of the trip or event; and (II) the amount of any additional revenue received by the recreation service provider for an add-on activity or an optional excursion that occurred on the Federal recreational lands and waters covered by the special recreation permit. (ii) The difference between— (I) the total cost paid by the participants of the trip or event for the trip or event to the recreation service provider, including any additional revenue received by the recreation service provider for an add-on activity or an optional excursion that occurred on the Federal recreational lands and waters covered by the special recreation permit; and (II) the sum of— (aa) the amount of any revenues from goods, souvenirs, merchandise, gear, and additional food provided or sold by the recreation service provider to the participants of the applicable trip or event