Any agreement on the part of a party hereto to (a) extend the time for the performance of any of the obligations or other acts of the other parties hereto, (b) waive any inaccuracies in the representations and warranties contained herein or in any document delivered pursuant hereto or (c) waive compliance with any of the agreements or conditions contained herein shall be valid only if set forth in a written instrument signed on behalf of such party, but such extension or waiver shall nor operate as a waiver of, or estoppel with respect to, any subsequent or other failure.