Richard who loves mountain biking is a student studying Accountancy at NUN. On 01/03/2019, Richard saw an advertisement made by Leo in a flyer offering to sell his mountain bike at a price of RM6,000. On 02/03/2019 he wrote a letter to Leo accepting the offer. Unfortunately, the letter was only received and read by Leo on 05/03/2019. Cynthia saw the same advertisement made by Leo in a magazine on 03/03/2019. She immediately faxed a letter to Leo proposing to purchase the bike at a cost of RM5,000.00. Leo only read the fax on 04/03/2019 and replied that he would accept Cynthia's proposal if the price is RM5,500. Cynthia agreed. Prior to this, Cynthia had made a proposal to purchase a similar bike at RM6,000 from Mr. Tony on 01/03/2019. Since the price offered by Leo is cheaper than Mr. Tony, she sent a letter revoking her proposal on 03/03/2019 which Mr. Tony received and read on 06/03/2019.Advise Richard, Cynthia and Mr. Tony and discuss on the validity of the agreement that they have entered into