A firm that charges the maximum price without attracting competition from new entrants is

Analyze the question: The question asks which type of firm can charge the highest price without new firms entering the market and competing with it. This means there must be something blocking new entrants.

Explain the concept:

• Perfect competition: Many sellers, free entry and exit. Firms are price takers. If a firm charged more than the market price, it would lose all its customers, and abnormal profits attract new entrants. So it cannot charge a maximum price.
• Monopolistic competition: Many sellers with differentiated products (e.g. bakeries, salons). Entry is easy, so abnormal profits are competed away in the long run.
• Monopoly: A single seller with high barriers to entry (legal control, ownership of key resources, huge capital costs, patents). It is a price maker, so it can set a high price and keep earning abnormal profit, because new firms cannot easily enter.
• Oil firms: This is just an industry, not a market structure. Oil firms could be monopolistic, oligopolistic, or competitive, so it does not define the type of firm described.

Step-by-step solution:

1. The key phrase is "maximum price", which means the firm has price-setting power.
2. "Without attracting competition from new entrants" means barriers to entry exist.
3. Only a monopoly has both features: it is a price maker and is protected by barriers to entry.
4. Perfect and monopolistic competition both have free or easy entry, so they are eliminated.
5. "Oil firms" is not a market structure, so it is eliminated.

Correct answer: C. Monopolistic firm

Exam tip: When you see "barriers to entry" or "price maker without new competitors", think monopoly. Remember: Monopoly = one seller + blocked entry + price control. Also, be careful of options that name an industry (like "oil firms") instead of a market structure.