Correct answer: Kq/r - Kq/r1
A conductor is an equipotential; inside it the total potential is constant and equals the potential at its centre, where the point charge contributes Kq/r and the induced charges contribute zero (they sum to zero net charge and centre is equidistant in the net-zero sense), giving V_total = Kq/r. At point P the point charge q alone contributes Kq/r1. Since V_total = V_q + V_induced, the induced part is V_induced = V_total - V_q = Kq/r - Kq/r1.