Grace is deciding between three potential activities on Saturday evening:

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

Activity 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.

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

a) Which activity should Grace choose? Explain.

b) What is Grace's opportunity cost of going to the movies?

c) Grace received a phone call from her friend informing her that Ken will also be joining the dinner, soshe re-evaluated the value of the dinner and decided to attend. What is the minimum value of this outing? Explain.