Use the following to answer question 18: A cement manufacturer has supplied the following data: Tons of cement produced and sold 220,000 Sales revenue $990,000 Variable manufacturing expense $308,000 Fixed manufacturing expense $260,000 Variable selling and administrative expense $165,000 $83.000 $174,000 Fixed selling and administrative expense Net operating income The company's contribution margin ratio is closest to: Select one: a. 52.2% b. 43.8% C. 68.9% d. 17.6%