You have two options for how to spend the afternoon. You can either go see a movie with your roommate or work as a tutor for the Math Department. From experience, you know that going to see a movie gives you $20 worth of enjoyment, and with your student discount, a movie ticket only costs $12. If you spend the afternoon working as a math tutor, you will get paid $45. On a typical day, you wouldn't be willing to spend the afternoon working as a math tutor for less than $35. What is your opportunity cost of seeing a movie this afternoon?