definiens: shall mean the total of the gross amount billed or invoiced to Third Parties for the sale of a Product in the Field ( ), less : ( a ) rebates granted and allowances, trade, quantity or cash discounts actually allowed and taken ; ( b ) retroactive price reductions imposed by government authorities ; ( c ) fees, commissions or rebates lawfully paid pursuant to contracts with group purchasing organizations ; ( d ) amounts actually repaid a Third Party by reason of rejection or return of defective Product ; and ( e ) a fixed amount representing upcharges paid by Third Parties as part of a reagent agreement plan or similar arrangement equal to five and one -half percent ( 5.5 % ) times the excess of ( i ) Gross Sales over ( ii ) deductions made under subsections ( a ) through ( d ) above ; provided, however, that if any Product is sold by [COMPANY] or its Affiliates in combination with other components which have commercial utility other than use in combination with such Product ( together, a ), Net Sales of such Product shall be the gross invoiced price of such Combination Product billed to customers by [COMPANY] or its Affiliates, less the allowances and adjustment referred to above, multiplied by the fraction A/(A+B ), where A is the gross selling price of the Product sold separately during the period in question, and B is the gross selling price of such other components sold separately during the period in question ; provided, further, that if a ny Combination Product is sold by [COMPANY] or its Affiliates and the gross selling price for the Product or such other components is not determinable, then the gross amount billed or invoiced to Third Parties for the sale of such Product shall be deemed to b e an amount equal to the percentage of the gross sales price, less the allowances and adjustments referred to above, for the Combination Product which is equal to the percentage of the fair market value of the Product and such other components in the Combi nation Product represented by the fair market value of the Product . ” 3