XYZ Inc. sells a single product for $30 per unit. Variable production costs are $18 per unit. Fixed overhead costs amount $20,000 per month. Variable selling costs are $3 per unit. Fixed selling costs are $4,000 per month. Last month, the company produced 10,000 units and sold 5,000 units. What is the company's margin of safety? a. $40,000 b. $160,000 c. $70,000 d. $20,000