A potential difference Δ V ΔV exists between the inner and outer surfaces of the membrane of a cell. The inner surface is negative relative to the outer surface. If 2.20 × 10 − 20 J 2.20×10−20 J of work is required to eject a positive potassium ion (K + ) (K+) from the interior of the cell, what is the magnitude of the potential difference (in millivolts) between the inner and outer surfaces of the cell?