The correct answer to this question is For school. The answer to this question could be found by listening to the included audio. Instead of laying around or partying, most students during the summer work to save money for various things.
With the growing costs of college, most of people's money is going to school. In the long run, Paul is making the best decision to use the money he earns during the summer for school. This way, he can ensure he has enough money for his tuition, books, supplies, and any room and board that he needs to pay.