The inner sphere has a net charge of +6 C and the shell has a net charge

The inner sphere has a net charge of +6 μC and the shell has a net charge of +6 μC.

A conducting sphere (radius a) is placed at the center of a conducting spherical shell (inner radius b and outer radius c). The conductors are in electrostatic equilibrium. For the given charges: 

(a) Sketch a field line diagram. 

(b) Determine the charge on the inner and outer surfaces of the shell. 

(c) Sketch a graph of E_r, the radial component of the field, as a function of r. (E_r > 0 if the field is radially outward and E_r < 0 if the field is radially inward.)