a) Consider a gaussian surface which is just outside the inner surface of the spherical shell. E is zero everywhere on that surface.
b) E remains zero on the surface of part a). Can there be any change?
c) E must still remain zero on the surface of part a).
d) What would make them change?
Use a cylindrical gaussian surface, coaxial with the actual cylinders. Remember that the electric field is everywhere zero in a conductor.
At all points where there is an electric field it is radially outward. For each part of the problem use a spherical gaussian surface, centered about the center of the actual spheres, and passing through the point where the field is to be found.
a) Charge enclosed is q (r/a)3 for r < a.
b) Charge enclosed is q for a < r < b.
c) The shell is conducting.
d) Charge enclosed is zero.
e) For b < r < c , the electric field must be zero; a gaussian sphere with this radius must enclose no net charge.
a) So what exactly does the conducting wire do when it joins the other two conductors -- think electrostatics!
b) Use the result for the potential on a spherical conductor, V = kq/R.
c) Use the results of part b) for each sphere.