Leah has two options this Friday evening. She can either babysit for her professor's kids and earn $50 for the evening, or she can join some friends for dinner and a movie. The movie will cost $25 for ticket and concessions and dinner usually runs around $20.Her roommate has a coupon for 50% off dinner at their favorite restaurant and is trying to convince Leah to come with them rather than babysitting.

Which of the following is Leah's opportunity cost if she decides to go with her friends?

• The $50 she would earn from babysitting
• The $25 she will spend on movie ticket and concessions
• The $10 she will save using the 50% off coupon for dinner
• The difference between what she would earn from babysitting and what she would spend at dinner and the movies