I am struggling with the below question.

andy has just been offered an extra evening shift for 3 hours at coles. he would earn $100 if he takes it, however, he already plans to go with his mates and catch the latest Avengers movie, the movie ticket costs $20 what is the total opportunity cost for andy if he decided to go to the movies?

No sure if the opportunity costs would be the while $100 as he is giving up the opportunity to earn the $100 or is $120 ($100 plus the expense of going to the movies).

I am really struggling with economics at the moment.

Thank you