4. The following is Robin Corporation's contribution format income statement for the last month: Sales Variable expenses $1,500,000 $500,000 Contribution margin $1,000,000 Fixed expenses $600,000 Net operating income $400,000 The company has no beginning or ending inventories and produced and sold 50,000 units during the month. Required: A. What is the company's contribution margin ratio? B. What is the company's break even in units? C. If sales increased by 1000 units, by how much should net operating income increase? D. How many units would the company have to sell to attain target profits of $500,000? E. What is the company's margin of safety in dollars? F. What is the company's degree of operating leverage?