Kamryn is deciding between three potential activities on Saturday evening:

1) Staying at home and watching her favorite television show, an activity that she values at $18 and that entails no out-of-pocket costs.

2) Going to the movies with her sister to see the latest blockbuster action film, an activity she values at $30 and that entails $15 in out-of-pocket costs.

3) Going out to dinner with her best friend, an activity she values at $40 and that entails $23 in out-of-pocket costs.

What is Kamryn's opportunity cost of going to the movies?

Relative to her next best alternative, what is Kamryn's economic surplus from going to the movies?