Laura, Heyma and Sam are students at a music academy in Malaysia. They are often to be seen playing their instruments in One Utama Shopping Centre, to entertain shoppers. One day, Laura is approached by her Uncle Arun who ask if they were prepared to play at his daughter's wedding later that year. Laura and her friends decide that it would be a good opportunity for them and agree to do so. Having played at the wedding, the 3 girls send Uncle Arun an invoice for RM300. Uncle Arun refuses to pay them, saying that he had not intended the arrangement to be binding, as he was simply giving them a formal opportunity to practice in public.

According to UK law, explain who is the offerror, offeree, promisor and the promisee.