The radius of a solid sphere is 21 cm. is . It is melted and made into a cube. In this process 20% of the material is wasted. The cube is melted to form a semicircle. In this process 20% of the material is wasted. The hemispheres are melted to form two spheres of two equal radii. Even 20% of the material was wasted in this process. What is the radius (in cm) of each new sphere?