A very thin insulating annulus (a disk with a hole) has an outer radius R, and an inner radius of R/2. There is a charge Quniformly distributed over the surface of the annulus. The z-axis of the annulus would be perpendicular to the surface of this paper, located at the center of the disk. Consider the center of the disk to be the origin. A.Find the potential as a function of distance zfrom the annulus, along the axis.