A sphere of radius R made up of Styrofoam (light polystyrene material) has a cavity of radius $$\frac{R}{2}$$. The centre of the cavity is situated at a distance of $$\frac{R}{2}$$ from the centre of the Styrofoam sphere. The cavity is filled with a solid material of density five times that of Styrofoam. Now, the centre of mass is seen to be located at a distance x from the centre of Styrofoam sphere, therefore x is