Scenario: Charlie sends a written offer to Morgan which says, "I hereby offer to pay you $400 if you bring me 600 apples, and 12 oranges." Morgan sends a reply that says, "I will bring you 600 apples and 12 oranges for $400 provided that you put up an advertisement for my business in your store."

Question: Do they have a valid contract?Please explain why or why not using application of law to facts.