A point charge 4q > 0 is placed at the center point O. There is a thick conducting spherical shell with inner radius R2 and outer radius R '2 centered at O. The thickness of this shell is R '2 − R2. Another larger thin concentric spherical shell has radius R3. The thickness of this shell is negligible. The thick shell is charged with a charge 3q and the large thin shell is charged with a charge 9q.