Two concentric spherical metal shells are insulated from each other and from the surroundings. The inner shell carries a charge \(+2 q\), and the outer shell carries a charge \(-q\). In electrostatic equilibrium, what is the charge on

(a) the outer surface of the inner shell,

(b) the inner surface of the outer shell, and

(c) the outer surface of the outer shell? 

\((d)\) The shells are then connected to each other by a metal wire. Do parts \(a-c\) for the situation obtained after electrostatic equilibrium is reached.