A hollow metal sphere has inner and outer radii of 7 cm and 10 cm radii. A point charge is located at the center is located at the center of the sphere. The surface charge density on the inside surface is -300nC/m2. The surface charge density on the exterior surface is +300 nC/m2. What are the strength and direction of the electric field at points 4, 8, and 12 cm from the center?