Ответ:
Here's the completed dialogue:
B: First of all, I'm going shopping on Saturday morning. **After** that I'm meeting some friends for lunch. What are **you** doing? What are you doing?
A: I don't **know** what I'm doing yet.
What about you, Sam? **Then** are your plans?
C: I'm going swimming in the morning. I'm going to a football match.
B: First of all, I'm going shopping on Saturday morning. **After** that I'm meeting some friends for lunch. What are **you** doing? What are you doing?
A: I don't **know** what I'm doing yet.
What about you, Sam? **Then** are your plans?
C: I'm going swimming in the morning. I'm going to a football match.
