Sales (30,000 units) $150,000 Variable costs 100,800 Contribution margin 49,200 Fixed manufacturing costs 24,000 Operating income 25,200 Interest 18,000 7,200 2,160 $5,040 600 Earnings before taxes Taxes (at 31%) Net income Shares outstanding This firm's break-even point is: O a. 18,000 units. O b. 7,142 units. O c. 14,634 units. O d. 4,800 units.