"Lego" is a famous brand of various toy products comprising plastic bricks that can interlock to form various shapes and objects. Mickey works at a bank, and in his spare time, he is a passionate Lego toy collector. Given that he is planning to move to a smaller apartment, he decided to downsize his Lego collection. With some reluctance, he decided to put up for sale his limited edition Lego "Star Wars Millennium Falcon" set (the "Lego Set"), which is a rare item no longer found in regular shops. A few weeks ago, on a Monday, Mickey listed the Lego Set for sale on "Brickety", an online marketplace where Lego enthusiasts can post listings to buy and sell second-hand Lego products. Mickey's listing on Brickety stated as follows: Limited Edition and Rare Lego Star Wars Millennium Falcon Set for Sale! Includes original box with building instructions Built once, but has since been dismantled and stored in box Asking price: $2,500 Will deliver to your preferred location in Singapore Mickey also provided his work email address with this listing, so that interested parties could contact him directly via email. Donald is Mickey's colleague. Although they both work at the same bank and can recognise each other at the workplace, they are not close friends. Donald is also an avid fan of Lego products, and he chanced upon Mickey's listing on Brickety on Tuesday (i.e., the day after Mickey posted his listing). Donald immediately recognised that this listing was posted by the "Mickey" that he knew, as he saw Mickey's work email address mentioned with the listing. Donald immediately sent Mickey an email to express his excitement on seeing the listing, and he also asked if Mickey would be willing to sell the Lego Set to him at the discounted price of $2,000, given that they were colleagues and knew each other. Mickey replied a day later (i.e., on Wednesday) via email, "That is too low for me. $2,500 is actually fair if you look at the market pricing for such a rare collectible. Let me know if you are still keen for $2,500?" Donald was extremely busy on Wednesday as he was preparing to travel to New York for a work trip. As a result, Donald only managed to read Mickey's email using his mobile phone as he was boarding his flight to New York on Thursday morning. Donald hurriedly typed out a response, "Fine, let's close this deal at $2,500. I will pay you the money and collect the item from you when I am back in the office next week." While Donald did click the "Send" button on his mobile mail application, he did not realise that the mobile network connection was poor, and the email was not successfully sent before the plane departed from Singapore. Donald did not have access to any Internet or Wi-Fi connection on the plane. Therefore, his email to Mickey was only sent out on Friday morning (based on the time in Singapore) when Donald arrived in New York. As Mickey did not receive any reply from Donald on Wednesday and Thursday, Mickey assumed that Donald was no longer keen to buy the Lego Set. Furthermore, on Thursday, Mickey received another email from a person called Daisy, who was willing to pay $2,500 for the Lego Set. Therefore, Mickey sold the Lego Set to Daisy on Thursday. On Friday afternoon, Mickey finally read Donald's email. Unfortunately, Mickey had already sold the Lego Set to Daisy, and Mickey felt that nothing could be done about it. When Donald returned to Singapore the week after and learnt of this development, he was very upset and protested strongly to Mickey, saying that they had already "sealed the deal".

(a) Explain whether there is a valid contract between Mickey and Donald for the sale of the Lego Set. In your answer, you should identify and discuss the four (4) elements of a contract. (This means that you should also state and define the four elements of a contract, discuss the relevant legal rules associated with them, and apply the legal rules with reference to the facts and circumstances described in the scenario.)