A person sees an item in a shop with a price displayed of 80. They enter the shop, and offer the shopkeeper 60, to which the shopkeeper accepts if the customer comes back at the end of the day with a bottle of wine and pays the 60 in cash. At the end of the day the customer returns, hands over the bottle and the cash and leaves with the item.Which part of the scenario above represents a counter offer in the context of contract law?