On January 1, a car salesman offered to sell an antique car to a collector for $35,000 cash on delivery. The collector paid the car salesman $100 to hold the offer open for a period of 25 days. On January 4, the collector called the car salesman and left a message on his answering machine, asking him whether he would consider lowering the price to $30,000. The car salesman played back the message the same day but did not reply. On January 9, the collector wrote the car salesman a letter, telling him that he could not pay more than $30,000 for the antique car, and that if the car salesman would not accept that amount, he would not go through with the deal. The car salesman received this letter on January 10 and again did not reply. The car salesman never heard from the collector again. When did the offer that the car salesman made to the collector on January 1 terminate