A thin, flat circular disk of radius \(R\) lies in the \(xy\)-plane, centered at the origin. The disk carries a non-uniform surface charge density given by \(\sigma(r) = \sigma_0 \left(\dfrac{r}{R}\right)^2\), where \(r\) is the distance from the origin and \(\sigma_0\) is a positive constant. What is the ratio of the electric potential \(V(R)\) at a point on the central axis at \(z = R\) to the electric potential \(V(0)\) at the center of the disk?