Carrie offered to sell a set of legal encyclopaedia to Antonio for $300. Antonio said that he would think about her offer and let her know his decision the next day. Norvel, who had overheard the conversation between Carries and Antonio, said to Carrie, “I accept your offer” and gave her $300. Carrie gave Norvel the books. The next day, Antonio, who had no idea that Carrie had already sold the books to Norvel, told Carrie that he would accept her offer. Has Carrie breached a valid contract with Antonio?