On September 1, GravemanGrillsmailed a purchase order to the Steel Suppliersfor 1,000 sheets of advanced, high quality 304 stainless steel at $50 per sheet.Graveman's purchase order also indicated that Steel Suppliers should deliver the sheetsat Stainless'sexpense by September 15.After receiving Graveman's purchase order, Steel Suppliers mailed a written acknowledgment, agreeing to all of Graveman's terms except that the price of the sheets will be $51 per sheet and that delivery will be on September 30. Steel's acknowledgment also contained a provision that limited Graveman'sright to refund to the first 30 days upon receipt of the goods.Do Graveman and Steel have a valid contract?Why or why not?