Mona owns a cleaning service. Because her friend Greg was recovering from surgery, Mona cleaned his home for six months for free. After Greg had recuperated from his surgery, he wrote Mona a note stating, "You've always been a great friend to me, Mona. In return for your kindness and generosity, I am going to pay you $500." A week later Mona and Greg had a falling out. Greg now refuses to pay Mona the $500. Is Greg obligated to pay Mona? Why?

Question 13 options:

No, Greg is not obligated to pay Mona because the $500 is a gift.

Yes, Greg is obligated to pay Mona because he promised in writing to pay Mona $500.

Yes, Greg is obligated to pay Mona because she provided a valuable service to him.

No, Greg is not obligated to pay Mona because, as Greg's friend, Mona had a preexisting duty to help Greg during his recovery.