A solid sphere has a radius 21 cm. It is melted to form a cube. 20% material is wasted in this process. The cube is melted to form hemisphere. In this process 20% material is wasted. The hemisphere is melted to form two spheres of equal radius. 20% material was also wasted in this process. What is the radius (in cm) of each new sphere?

• A. \(4.2\left( {\sqrt[3]{2}} \right)\)
• B. \(2.2\left( {\sqrt[3]{2}} \right)\)
• C. \(2.2\left( {\sqrt[3]{4}} \right)\)
• D. \(8.4\left( {\sqrt[3]{4}} \right)\)