7. (a) At a distance of d/5 from a positive charge, by what factor is the electric potential changed: (1) 1/5, (2) 5, (3) 1/25 or (4) 25? Why? (b) How far from a +2.0 uC charge is a point with an electric potential value of 15KV? (c) How much of a change in potential would occur if the point were moved to three times the distance?