10) You are faced with the following alternative choices on a Friday night: Choice A: Go to a concert, which costs $30. Choice B: Go to a party at a friend's house. Choice C: Go to the library and study economics. It turns out that Choice A is your most preferred activity, Choice B is your second most preferred activity, and Choice C is your least preferred activity, so naturally, you go to the concert. What is the oportunity cost of going to the concert? A) $30 B) $30 plus missing your friend's party. C) $30 plus missing your friend's party plus not studying economics at the library. D) Missing your friend's party plus not studying economics at the library.