Finding the electric field at a given point

[kirax105strike]

Homework Statement

I have a sphere with two thin concentric shells with radii R2 and R3 with charges q1 and q2. I am trying to find the formulas for find the electric field for A and B.

The Attempt at a Solution

I found C to be E = k * (q1+q2)/c^2 but I cannot seem to figure out the correct formulas for A and B. Here is a picture of the sphere http://imgur.com/cWS8r5G

 

[vanhees71]

Think about the symmetry of the problem and then use Gauss's Law!