CellMate Communications, an electronics store, and Meertex, a smart phone manufacturer, enter into an installment contract under which Meertex must deliver 100 of its newest model phones to CellMate every eight weeks. When Meertex delivers Textasy 8 to Meertex the week after the release of Meertex's highly anticipated Textasy 9, CellMate rejects the shipment. Has CellMate breached the contract?