The radius of base of solid cone is 9 cm and its height is 21 cm. It cut into 3 parts by two cuts, which are parallel to its base. The cuts are at height of 7 cm and 14 cm from the base respectively. What is the ratio of curved surface areas of top, middle and bottom parts respectively?

• A. 0.044537037037037
• B. 0.04380787037037
• C. 0.043854166666667
• D. 0.045972222222222