(4) (a) (4 points) Suppose an electric charge p(x, y) is uniformly spread on a disc of radius r around the origin. Use Maxwell's first equation (in a non-dimensional version) V.E= p. to prove that far away from the origin R > r, the field is proportional to R-1. Do not use the explicit formula for the electric field. Do use the fact that the electric field points towards the charged particle, and whatever symmetries this problem has. (b) (2 points) When we stated Coulumb's law in class, the field was proportional to R-2. What is the difference? Did we just disproved the laws of electromag- netism?