There is a negative charge of -q uniformy distributed on the surface of a hollow insulating sphere to the distance R from the center of the sphere. Inside the sphere just at the center, there is a positive point charge +q. a) Sketch a figure of the situation, and plot the field lines of electric fields inside the spherical cell. b) Assume a closed spherical surface following the symmetry of the insulating spherical cell. Determine the electric flux through this imagined surface. The radius of this surface is a < R. c) Determine the electric flux density outside the insulating sphere at distance r > R from the center of the sphere