Shells and a point charge A conducting cubical shell is inside a spherical conducting shell and they have non-negligible thicknesses as shown in the figure below. Spherical shell S carries a net charge of +2Q where Q > 0. Cubical shell C carries a net charge of ?2Q. The two shells share a common center. Also, a point charge +Q is fixed at the same center. The system is in electrostatic equilibrium.

\f(a) Find the net charge on the inner and outer surfaces of the two (one spherical and one cubical) shells. (b) For each of the four surfaces, state whether the charge per unit area is uniform or nonuni- form. If there is no surface charge at all, enter 0. Explain your answers. (c) Choose all the regions in which electric field should be zero? Explain your answers. (A) Free space outside the spherical shell; (B) Free space between spherical shell and cubical shell; (C) Free space between cubical shell and a point charge; (D) In the body of the spherical shell; (E) In the body of the cubical shell; (F) None of the above. (d) Now place a test point charge +q outside of the spherical shell at a distance, d, from the point charge +Q at the common center of shells. Find the magnitude of the force on the test charge due to other charges. For a good approximation, assume that the amount of charge q is sufficiently smaller than