On 1 ^stFebruary 2022, William wrote a letter to Roy offering to sell his cat, Comel, at the price of RM2000. William gave Roy until 10^thFebruary to accept his offer. Roy received the letter on 3^rdFebruary 2022 and posted a letter, accepting William's offer on 9th February 2022. William, however, has changed his mind about selling Comel. He posted a letter to Roy on 7^thFebruary 2022 revoking his offer. Roy received the letter of revocation on 10^thFebruary 2022, and William received Roy's letter of acceptance on 12^thFebruary 2022.

Advise Roy on whether a contract has been constituted. Support your answers with all relevant authorities, including case law, provisions of the statutes, and others.