provided that the costs of all tooling,dies and jigs in connection with manufacture of the parts shall be includes into said prices of the parts .Buyer and Seller shall review periodically and change if necessary,the prices for the parts upon mutual consent.Seller shall use its best efforts to reduce the prices of the products and to improve the quality of the products in order to remain the products competitive in price and quality. All changes of such prices and the effective date thereof shall be determined by both Parties in writing