Megan wished to sell her laptop. On 1 December 2019, she placed an advertisement in The Online News, a free digital newspaper, which listed details of her laptop, including its brand, age, model and condition. Further, she had also stated, "Special offer price of $1,000. WhatsApp: 8195 2828". On 3 December 2019, Megan received a WhatsApp message from Kate to enquire about the laptop. Kate was responding to the advertisement in The Online News. Kate asked Megan what was the highest offer that she had received for her laptop. Megan replied that she had received an offer of $700 but would only sell her laptop for not less than $900 since it was in mint condition. Kate then made an appointment to inspect the laptop on 7 December 2019. On 6 December 2019, Kate decided that she would buy Megan's laptop at her asking price of $900. She called Megan to inform her but the latter did not answer her call. In the meantime, Megan was negotiating with Harry who was also interested to buy her laptop. Later that day, Megan checked her phone for messages after her conversation with Harry. She received the following message from Kate, "Megan, I am agreeable to your offer price of $900 for the laptop. Please call or message me back to make arrangements for the payment and delivery of the laptop."

a)State the definition of a contract and ALL the elements required to form a valid contract.

b)Discuss and advise Megan whether she had an obligation to sell her laptop to Kate. In your answer, you should provide all relevant LEGAL PRINCIPLES and case laws to be APPLIED to the facts of the case to reach your CONCLUSION.

c)Advise Megan when she might be able to revoke an offer using case law