Mo Agrees to Provide Lawn Care Services to Judith in Preparation

Multiple Choice

Mo agrees to provide lawn care services to Judith in preparation for a summer birthday party Judith is holding for family and friends.The agreement requires that Judith pay Mo $250.00 for three hours' work.After completing approximately half of the job,Mo requests that Judith pay him an extra $50.00 because the cost of gasoline used for the rider mower had gone up significantly that morning.Judith agrees to pay the additional $50.00.Is she legally liable to do so?

A) Yes she is,because she told Mo she would pay him and he finished the job on the basis of her promise.
B) Yes she is,because the rising price of gas should be borne by Judith.
C) No she isn't,because Mo had an existing contractual obligation to perform the services for $250.00 and there is no consideration for the subsequent agreement to pay $50.00 more.
D) No she isn't,because Judith is promising to reward Mo for something he has previously done and the past consideration is no consideration.