Read the passages below and answer the question that follows. John loves to sleep late in the morning. He also knows that school is important. This morning, John chose to wake up and get to school on time. In doing this, he gave up the opportunity to sleep in. The opportunity cost of John's choice to go to school is two or three hours of sleep.

Ana loves to go camping with her family and is looking forward to their trip next weekend. Ana learns that her good friend is having a sleepover birthday party the same Saturday as the trip.

For Ana, what would be the opportunity cost of going to her friend's party? Why?