3 Consider total cost and total revenue given in the following table:

a Calculate profit for each quantity. How much should the firm produce to maximise profit?
b Calculate marginal revenue and marginal cost for each quantity. Graph them. (Hint: Put the points between whole numbers. For example, the marginal cost between 2 and 3 should be graphed at 2½.) At what quantity do these curves cross? How does this relate to your answer to part (a)?
c Can you tell whether this firm is in a competitive industry? If so, can you tell whether the industry is in a long-run equilibrium?