Sales (2,000 units @$25) Less: Variable Costs Contribution Margin Less: Fixed Costs Pre-Tax operating income $50,000 20,000 30,000 18,000 12,000 a. Calculate the break-even number of units. (Show your work). b. Calculate the break-even in sales dollars. (Show your work). c. Calculate the margin of safety. (Show your work). d. Calculate the number of units that must be sold to earn a pre-tax profit of $20,000. (Show your work)