The following is Knox Corporation's contribution format income statement for last month: Sales Less: variable expenses Contribution margin Less: fixed expenses Operating income $900,000 300,000 500,000 400,000 $100,000 The company has no beginning or ending inventories. The company produced and sold 10,000 units last month. If sales increase by 200 units, by how much should before-tax profits increase? $16,000. O $5,000 O $12,000. $10,000