Finding Expressions for Electric Fields with Radius

kgal

1. The problem statement, all variables and given/known data
A solid nonconducting sphere of radius a has a has a total charge +Q uniformly distributed throughout its volume. The surface of the sphere is coated witha avery thing (negligable thickness) conducting layer of gold. A total charge of -2Q is placed on this conducting layer.
Use Gauss's Law to do the following:
a. Find the expression for the electric field E(r) for r<a (inside the sphere, up to and excluding the gold layer).
b. Find the expression for the electric field E(r) for r>a (outside the coated sphere, beyond the sphere and the gold layer).


2. Relevant equations

Eflux = ∫E dot dA = Q/ε0
A sphere = 4∏r^2

3. The attempt at a solution
I got part a. like this:

Eflux = ∫E dot dA (electric field is constant because uniformly distributed) = EA = E*4∏r^2 = Q/ε0.
solving for E = Q/ 4∏r^2ε0

is this right?

for part b. I am lost....