Suppose a single firm can produce 100 units at an average cost of $15. If two firms produce 50 units each, the total cost rises to $2,500. Which of the following could be true about this market? a. It is a natural monopoly. b. The demand for this product will be higher if there are two firms producing the product than if there is only one. c. Neither firm can make a profit. d. It is more efficient to have two firms so they each have a competitor