CityGas is the only supplier of heating gas in Country K. It has a total cost function of C = 240 + 15Q.

a. Find the marginal cost of CityGas. Show your steps.

b. Based on your result in (a), show the marginal cost of CityGas in a graph.

c. Making use of the graph in (b), show the profit-maximizing output level, and price of CityGas. (No calculation is required).

d. i. Identify one key feature of the average cost of CityGas. Explain why this implies CityGas is a monopoly in the market of heating gas in Country K.

ii. Besides (d)(i), briefly explain TWO other causes of monopoly power in general.