Sylvia and Carmen have a valid contract. Sylvia tutors Carmen's son, Daniel, in English for 10 hours a week. Carmen pays Sylvia $20/hour. Carmen pays every 2 months. Sylvia usually tutors Daniel for 2 hours a day Monday - Friday. Because of a personal problem Sylvia is unable to tutor Daniel on Friday. She does allow Carmen to take him on Saturday. Carmen knows that Sylvia charges $30/hour on Saturdays. After 2 months Sylvia sends Carmen a bill for $1760 (assume a month has 4 weeks). Carmen refuses to pay the bill arguing that she only owes $1600.

A]. What is Carmen's best argument?

B] Assume Sylvia and Carmen agree on $1680 and Carmen pays the $1680. What does this agreement represent? Explain.