Todd leaves his babysitter, Zach, a voice mail message saying, "I need someone to watch little Joey and Hilary on Friday night. If you can babysit on such late notice, I'll pay you an extra $40 on top of your usual rate. If I don't hear from you by 5 p.m. tomorrow, I'll assume we have a deal." If Zach does not call back, has a contract been created?