The figure shows a spherical shell with uniform volume charge density $\rho$ = 2.05 nC/m$^3$, inner radius a = 9.30 cm, and outer radius b = 2.3a. What is the magnitude of the electric field at radial distances (a) r = 0; (b) r = a/2.00, (c) r = a, (d) r = 1.50a, (e) r = b, and (f) r = 3.00b?