Ali decided to sell his vintage Rolls-Royce car. He placed an advertisement in Car Fans magazine on 1 December. The advertisement stated: For sale: vintage RR Corniche, 1970s. In excellent condition and only 50,000 miles. Serious offers only. Price: $600,000.' The advertisement went on to give a PO Box number and an email address. Barry saw the advertisement and was very interested in purchasing the car. As he did not own a computer, he sent a letter on 4 December to Ali's PO Box, stating that he would be willing to purchase the car for the quoted $600,000. The following day, 5 December, Cathy also saw the advertisement. She immediately emailed Ali, asking him if he had sold the car yet, and suggesting that if he had not, she would buy it for $500,000. Later that day, Ali replied and told Cathy that he had not sold the car, but would be willing to let her have it for $550,000. Cathy did not have the extra $50,000 that Ali had asked for, and so emailed him asking if she could pay $500,000 upfront and the remaining $50,000 next month. On 6 December, David emailed Ali at 11am and enquired after the car. Ali replied, asking for $550,000. At 3pm, Cathy found out that she had won $50,000 on a lottery ticket. She immediately emailed Ali, asking him to disregard her previous email and telling him she wanted to accept the price of $550,000. At 5pm on 6 December, David replied to Ali's email agreeing to buy the car for $550,000. The next day, 7 December, Barry's letter arrived in Ali's PO Box. Required: Advise Ali whether any valid contracts have been made for the sale of the car