The two spheres one is hollow and other is solid where the hollow sphere has a big hole due to which the outer & inner radius is approximately equal & it is also equal to radius of solid sphere. The charge of hollow sphere is "q" & charge of solid sphere is neutral hence find the TNEI of the solid sphere?
The answer is q/3 because the solid sphere acquires the one third part of the solid sphere making an angle of 120 degrees.