Knight is the owner of Armour Heights Subdivision. On September 1, he offered in writing to sell Lot#3 in the subdivision to Archer for $15,000; on September 2, Archer accepted the offer in writing and delivered her acceptance in person, by car. On September 4, Knight telephoned Archer to say that he had just learned that a shopping centre was going to be built in the subdivision near Lot #3 and that he now wanted to have $22,000 for each of the lots, including Lot #3. Archer, equally excited about the news, agreed to change the price stated in the written contract from $15,000 to $22,000 and wrote her initials on the date opposite the change. Later, Archer tendered a cheque for $15,000 "in full settlement of the amount owing for Lot #3 per our agreement of September 2." Knight deposited the cheque and sued Archer for an alleged $7,000 balance owing. a. Identify the legal issue (s). b. State the relevant legal rule(s) and apply them to the facts. c. State the conclusion.