Frank Says to Mary,"If You Wash Every Window in My

Multiple Choice

Frank says to Mary,"If you wash every window in my house today,I'll pay you $200.I don't care if you do it,but there is $200 in it for you if you do." Mary washes 12 of the 20 windows in Frank's house by 2:00 p.m.At this point:

A) Frank can revoke his offer to pay Mary the $200 for washing the windows.
B) Mary is obligated to finish washing the windows.
C) Frank cannot revoke his offer to pay Mary $200 for washing the windows.
D) no contract can be established based upon the given facts.
E) Frank and Mary have a formal, executed contract.