Answer
see solution
Work Step by Step
In electrostatic equilibrium, the charges are not in motion. If there were a nonzero electric field inside the conductor, then there would be a force on the free electrons and they'd accelerate. Thus there is no electric field inside the conductor. But this also implies that there are no free electrons inside the conductor or else they'd be creating an electric field. So all of the free electrons must be located on the surface of the conductor.