21. Wellcom Corporation has the following sales mix in units for its three products: A, 20%; B, 35%; and C, 45%. Fixed costs total $400,000 and the weighted-average contribution margin is $100. How many units of product A must be sold to break-even? A. 800. B. 4,000. C. 20,000. D. An amount other than those above. E. Cannot be determined based on the information presented