A firm is a natural monopoly if: a. any entrant would have the same costs.
b. its profit does not increase with output.
c. one firm can produce the total output of the market at lower cost than two or more firms could.
d. it has no fixed costs.
e. its marginal revenue is increasing faster than average costs.

c. one firm can produce the total output of the market at lower cost than two or more firms could.

Explanation:

A monopoly is a market structure which is typically characterized by a single-seller who sells a unique product in the market by dominance. Thus, it is a market structure wherein the seller has no competitor because he is solely responsible for the sale of unique products without close substitutes. Any individual that deals with the sales of unique products in a monopolistic market is generally referred to as a monopolist.

For example, a public power company is a monopolistic business firm because they serve as the only power utility provider to the public. Also, a public power company refers to a company that provides power (electricity) utility to the general public of a society.

Hence, a firm is a natural monopoly if one firm can produce the total output of the market at lower cost than two or more firms could.

answer: 11/12

step-by-step explanation: 4 1/4 and 3 1/3 is equivalent to 4 3/12 and 3 4/12. 4 3/12 - 3 4/12 =11/12