Audits by FOB. Achillion shall keep, and shall require its Affiliates and sublicensees to keep, records of the latest three (3) years relating to gross sales, Net Sales and all information relevant under Sections 6.4(c), 6.6 and 6.7. For the sole purpose of verifying amounts payable to FOB, FOB shall have the right no more than once each calendar year, at FOB’s expense, to review, together with FOB’s accountants, such records in the location(s) where such records are maintained by Achillion and its Affiliates and sublicensees upon reasonable notice and during regular business hours. Prior to any review conducted pursuant to this Section 6.5(b), FOB’s accountants shall have entered into a written agreement with Achillion limiting the use of such records to verification of the accuracy of payments due under this Agreement and prohibiting the disclosure of any information contained in such records to a Third Party and to FOB for a purpose other than as set forth in this Section 6.5(b). Results of such review shall be made available to Achillion. If the review reflects an underpayment to FOB, such underpayment shall be promptly remitted to FOB, together with interest calculated in the manner provided in Section 6.7. If the underpayment is greater than five percent (5%) of the amount that was otherwise due, FOB shall be entitled to have Achillion pay all of the costs of such review and such review shall not count as one of the reviews FOB is entitled to conduct hereunder.