You need to decide:Is it a valid contract?

Luke is a 21-year-old college student who has been having a pretty wild time for thelast couple of years. He goes to visit his grandmother, and she says, "Luke, I'm distressed at yourlifestyle. You know I'm not going to be around forever, and before I die, I'd like to know that youhave turned your life around and given up your wild ways." Luke feels bad. He enjoys partying asmuch as the next guy, but he really loves his grandmother and cares about her opinion of him. SoLuke tells his grandmother that he will change his behavior.About six weeks later Luke is visiting his grandmother again and announces that he has given upall of his bad habits. Grandma is thrilled. She says, "I am so proud of you for giving up smoking,illegal substances, alcohol, and gambling! In fact, I want you to have a reward: I will give you thedeed to my house." She even writes down her intentions on the back of a paper placemat from herlunch tray. She writes: "I promise to execute a warranty deed conveying ownership of my houseto my grandson, Luke, in exchange for his virtuous behavior over the last 6 weeks." Grandmasigns and dates the placemat and has Luke sign it, too. Luke is delighted and makes plans to moveinto the house. But unfortunately his grandmother has a stroke before she can execute the deed inhis favor. She is now in a vegetative state and cannot communicate. Grandma had signed aDurable Power of Attorney giving control of her affairs to Aunt Clarice. Luke asks Aunt Clarice ifshe will execute the deed to convey Grandma's house under the contract. Aunt Clarice says,"Contract??! What contract?! If you think I am going to give you a $200,000 house just becauseyou decided to behave in a responsible, civilized manner, you're crazy!"

Please tell me whether Luke can enforce the agreement he made with his grandmother. Why or why not?