Lizzo is a well$-$known musician signed with Atlantic Records. She entered into a contract and agreed to play Mark's private Halloween party for $$10,000.$ One week before Halloween, the Outside Lands Festival reached out to Lizzo and offered her $$25,000$ to play a show over Halloween weekend. Lizzo called fellow Atlantic Records musician, Bruno Mars, and he agreed to play Mark's private Halloween party with his friend Anderson $.$Paak. Lizzo then notified Mark that she would not be able to play the show but Bruno and Anderson would perform in her place. Assume that Lizzo and Bruno Mars$/$Anderson $.$Paak play unique types of music The contract that was entered into between Lizzo and Mark does not specifically reference this sort of issue.

Part $1(5$ points$)$: What is the legal term for Lizzo's attempt to substitute her contractual obligation to perform at Mark's Halloween party with a performance by Bruno Mars? Be specific and use concepts discussed in this unit in your answer.

Part $2(4$ points$)$: Does Mark have to accept this attempted substitution? Be specific and use legal reasoning and concepts discussed in this unit to explain your answer.

Part $3(3$ points$)$: Suppose there was a provision in the contract that allowed Lizzo's contractual obligation to be substituted by another Atlantic Records artist. How would this new fact affect your analysis? Be specific and use legal reasoning to explain your answer.