The following is Knox Corporation's contribution format income statement for last month: Sales Less: variable expenses Contribution margin Less: fixed expenses Operating income $900,000 300,000 600,000 400,000 $200,000 The company has no beginning or ending inventories. The company produced and sold 10,000 units last month. How many units would the company have to sell to attain after-tax profits of $72,000, assuming it is subject to a 40% income tax rate? 9,440 units. 11,600 units. 10,400 units. 13,111 units