Dave, a billionaire, is selling his large collection of luxury cars

Dave, a billionaire, is selling his large collection of luxury cars. Fred, his assistant, is helping him with this task. Bill, Dave’s uncle, hears of this and has always wanted the one Maserati in Dave’s collection. Bill writes to Dave and says: ‘I will give you $200,000.00 for the Maserati. If I hear nothing from you by next Saturday, I will consider it mine’. Fred does not know of the letter from Bill and sells the Maserati to Sally. When Bill finds out, later, he is furious and demands the car be delivered to him because Dave has not rejected his offer and the deadline in his letter has expired.
Explain, with reasons, whether Bill has a right in law, to demand that the Maserati be delivered to him.

Your argument should be supported by appropriate legal authorities (in this instance, relevant case law).