I'm struggling in this question, please help me explain. Thank you so much!

1. Describe the types of barriers that prevent entry into a monopoly market.
2. Fast-food stores often charge higher prices for their products in high-crime areas than they charge in low-crime areas. Is this an act of price discrimination? Why or why not?
3. Explain why a monopolist wants to price discriminate.
4. What is the difference between perfect and third-degree price discrimination?