A hollow metal sphere has $7$ cm

and $10$ cm

inner and outer radii, respectively, with a point charge at its center. The surface charge density on the inside surface is $100$nC$/$m$2$

$.$ The surface charge density on the exterior surface is $+100$nC$/$m$2$

What is the strength of the electric field at point $4$ cm

from the center? What is the strength of the electric field at point $8$ cm

from the center? What is the strength of the electric field at point $12$ cm

from the center?