The following is last month's contribution format income statement: Sales (12,000 units) Less: variable expenses $1,200,000 $700.000 $500,000 $300,00 $200,000 Less: fixed expenses Operating income What is the company's margin of safety in units? o a. 4,800 units b. 12,000 units C. 3,000 units d.7,200 units