The claimants offered to supply a machine tool to the defendants for ￡75,535. However, the quotation included a term which would entitle the sellers to increase this price (price-variation clause). The defendants accepted the offer on their own standard terms which did not provide for any variation of their quoted price. The claimants acknowledged the order. When the machine was delivered, the claimants claimed an extra ￡2,892 which the defendants refused to pay. The Court of Appeal held that the defendants had not unconditionally accepted the original offer. They had made a courter-offer which had been accepted by the claimant. The defendants' terms governed the contract. The claimants' action to recover the increase in price, therefore, failed.要求：description of the fact；the main legal issues and arguments and the decision in the case，写中文就好了，最好给我翻一下这个案例的意思