Asphere of radius a in free space contains charge of density rhov=rho0r/a, where rho0 is a constant. (a) find the electric field intensity, ei, inside the sphere. (b) find the electric field intensity, eii, outside the sphere. (c) a spherical shell of radius b is positioned concentrically around the sphere. what surface charge density, rhos, must exist on the shell so that the electric field at locations r > b is zero? (d) what electrostatic force per unit area is exerted by the solid sphere on the spherical shell?