A negative point charge -Q is at the center of a hollow insulating spherical shell, which has an inner radius R1 and an outer radius R2. There is a total charge of +3Q spread uniformly throughout the volume of the insulating shell, not just on the surface. What is the electric field at postion r away from the center? Use e0 as the electric constant. (a) When r is less than R1 X (b) When r is between R1 and R2 (c) When r is larger than R2