A firm producing poultry feed finds that the total cost C in dollars for producing and selling x units is given by C = 20x + 100. Management plans to charge $24 per unit for the feed. a. Graph the cost function and the revenue function together to show the break-even point. b. How many units must be sold to break even? c. What is the profit if 100 units of feed are sold? d. How many units must be sold to produce a profit of $900?