If fixed costs are $450,000, the unit selling price is $75, and the unit variable costs are $50, what are the old and new break-even sales (units) if the unit selling price increases by $10? a. 6,000 units and 5,294 units b. 18,000 units and 6,000 units c. 18,000 units and 12,858 units d. 9,000 units and 15,000 units