Hello, could someone help me solve question b), please? My module is Business Law. Thank you very much!

Question 3 Arthur placed an advertisement in WeSell, an online marketplace, to sell his laptop. Ben saw the advertisement on 1 October and sent Arthur the following message Hi Arthur. Your laptop still available? How much? Arthur replied Yes. Someone wanted to buy for $500 but I am not selling. Still very good condition. What is your price?" Ben responded that he would pay $600. Arthur replied that the amount was too low because he had bought the laptop just 2 months ago and it was in excellent condition and came with a wireless mouse. He went on to say that he was prepared to sell the laptop for $700 provided Ben revert to him by 4 October by mail, enclosing a cheque of $600, with the balance to be paid on collection of the laptop. Ben sent the following message to Arthur Let me consider your offer. I will get back to you and send you my cheque if I am buying. Thanks. On the morning of 3 October, Arthur changed his mind about selling his laptop. He typed a message to Ben to inform him that he would not be selling his laptop but forgot to send it out. In the meantime, Ben decided to buy Arthur's laptop. On the afternoon of 3 October he sent out a cheque of $600 to Arthur at the address provided by Arthur. He double- checked to ensure that he attached the correct amount of postage. He included a note that he would be available to collect the laptop on 7 October. Required: (a) Shtetetre-definition ofercontractament later the elements requireditorformatie contract. (b) Discuss and advise Arthur whether he has an obligation to sell his laptop to Ben. In your answer, you should provide all relevant legal principles with supporting cases. (c) Exploimiliyour cars wer wenidbe different sitatertiterrored remembered to street his message to Bonomthe morning