Peter wishes to sell his old lounge furniture set in order to make room for the new one that he has just purchased. Peter posts an advertisement online to sell the old couch. The advertisement reads "Lounge furniture set for sale, from $3,000. Delivery not included". The next morning, Saturday 1 March, Marina responds to Peter's advertisement by text message offering to buy the couch for $2,800. Marina leaves her phone number for Peter and asks that he calls her to discuss the offer. Later on 1 March, Peter telephones Marina and tells her that the price for the couch is $3,000 plus $100 delivery fee. Marina asks if she can have a little time to think about the offer and Peter says, "Certainly. I will leave the offer open for 7 days until Saturday 7 March. Please pay $100 deposit by the end of the day to my bank account" Peter gives Marina his bank details. On Monday 3 March, Marina posts a letter to Peter agreeing to buy the couch for $3,000 plus $100 delivery fee. She also attaches a cheque for the deposit ($100). Two days later, on Wednesday 5 March, Peter is having coffee with a close friend Racheal. Peter explains that he is selling his old furniture set. Racheal is interested in the furniture and offers Peter $3,000 in cash for the couch and says she will pick it up that day. Peter accepts and immediately rings Marina and to tell Marina that she has sold the couch to Racheal. Marina does not answer the phone, so Peter sends her a text message explaining that he has sold the couch. REQUIRED: With reference to relevant legal principles, use the IRAC legal problem-solving approach to advise Peter as to his contractual obligations to Marina and Racheal in respect to the sale of the furniture set. Please explain fully, using relevant legal authority. Please, provide two relevant cases/precedents in Australian Law.