The Purchase Agreement, as amended by this Amendment, constitutes the full and complete agreement and understanding between Seller and Purchaser and shall supersede all prior communications, representations, understandings or agreements, if any, whether oral or written, concerning the subject matter contained in the Purchase Agreement, as so amended, and no provision of the Purchase Agreement, as so amended, may be modified, amended, waived or discharged, in whole or in part, except by a written instrument executed by Seller and Purchaser.