3. + 2+ ++ + xx × Suppose the nonconducting sphere of Example 22-4 has a spherical cavity of radius centered at the sphere's center (Fig. 22-32). Assuming the charge Q is distributed uniformly in the "shell" (between = and r=), determine the electric field as a function of r for (a) 0 <r<, (b) <r<r, and (c) r>ro. ro + ×× ++ + + x 4. Suppose in Fig. 22-32, Problem 29, there is also a charge q at the center of the cavity. Determine the electric field for (a) 0<r<r, (b) r<r<ro, and (c) r>ro.