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.