7
b) 1. Susan's new to the school
2. I'm 14 years old
3. They're in Room E
4. He's my best friend
5. You're in Grade 7
c) 1. Susan isn't new to school
2. I'm not 14 years old
3. They aren't in Room E
4. He isn't my best friend
5. You aren't in Grade 7.