Josh, a second-year MBA student, takes three hours off one evening and uses his car to go to a movie with a friend. A ticket to the movie costs Josh $8, gasoline for the trip costs $3, and Josh passed up tutoring a student that night for $20 an hour. He could also have used the three hours to work as a grader for a professor for $15 per hour. What is Josh's economic cost of going to the movie?Enter a single number.