After the concert discussed in Problem 2-3 is over and you and your friend are traveling home, you discuss how each of you might otherwise have used the four hours devoted to attending the concert.

The four hours could have been used to study, to watch a streaming video of a sporting event, or to get some extra sleep. Your friend decides that if she had not spent four hours attending the concert, she would have chosen to study, and you reply that you otherwise would have watched the streaming video. Identify the relevant opportunity costs for you and your friend for allocating your four hours to attending the concert.

Explain briefly.