Al regularly rehearses accordion music on his back deck with members of his musical troupe, the Carlinville Lame Band. Practicing on his deck saves him the $500 per year it would take to rent a rehearsal place. Unfortunately, practicing on his deck keeps his neighbor, Marcy, awake at night. The value of Marcy's lost sleep is $600 per year.

1. What type of externalities is this?
2. Is it efficient for Al to keep rehearsing on his deck? Explain your answer.
3. Suppose the law says that it is legal for Al to rehears on his back deck, how much is Marcy willing to pay to get him to stop?
4. Given part c), what is the minimum amount of money Al is willing to accept for his silence?