In negotiations preliminary to the sale of Argentine hare skins by Colin & Shields Ltd. to Hartog, the parties had discussed price on the basis of price per skin, the way in which Argentine hare skins are generally bought and sold. Afterwards, Colin & Shields wrote to Hartog and offered to sell him 10,000 Argentine hare skins at CDN $10 per pound. There are approximately three pieces in a pound of Argentine hare skins. When Colin & Shields realized they had mistakenly quoted a price in terms of