E5. Suppose you find $20. If you choose to use the $20 to go to the football game, your opportunity cost of going to the game is a. nothing, because you found the money. b. $20 (because you could have used the $20 to buy other things}. c. $20 (because you could have used the $20 to buy other things) plus the value of your time spent at the game. d. $20 (because you could have used the $20 to buy other things) plus the value of your time spent at the game, plus the cost of the dinner you purchased at the game. e. none of the above