I’m studying for my Psychology class and don’t understand how to answer this. Can you help me study?

Imagine that you are on the subway going to school. A very neatly dressed man suddenly stands up singing his heart out. He is singing very loudly his favorite opera song but is not showing any signs of danger towards others. People are staring at him and laughing, but the man is oblivious to those around him. He now starts dancing on the subway knocking people over.

1. Is this normal behavior?

2. Does his behavior indicate signs of mental illness? Why or why not? (hint: What

do you need to know before determining that his behavior is abnormal?)