A solid insulating sphere of radius \(R\) contains a non-uniform distribution of positive charge. The total charge enclosed within a concentric spherical surface of radius \(r\) (for \(r \le R\)) is given by \(q_{\text{enc}}(r) = Q \left(\dfrac{r}{R}\right)^4\), where \(Q\) is the total charge of the sphere. Which of the following best describes the magnitude of the electric field \(E\) as a function of distance \(r\) from the center of the sphere for all \(r \ge 0\)?