Leonardo contracts to paint Monets two-story house for $4,500. Monet realizes that he will not have sufficient money, so he transfers his rights under this agreement to his neighbor, Raphael, who has a three-story house. Raphael notifies Leonardo that the contract between Leonardo and Monet has been assigned to him and demands that Leonardo paint his house for $4,500. Is Leonardo required to do so? Discuss.

Assume that Leonardo agrees to the assignment of the house-painting contract to Raphael. After, Leonardo fails to perform the contract to paint Raphael's house. Raphael sues Monet for damages. Is Monet liable? Discuss.