A uniform solid cylinder of mass $$M = 2\,kg$$ and radius $$R = 10\,cm$$ is connected about an axis through the centre of the cylinder to a horizontal spring with spring constant $$4\,N/m$$. The cylinder is pulled back, stretching the spring $$1\,m$$ from equilibrium. When released, the cylinder rolls without slipping. What is the speed of the center of the cylinder when it returns to equilibrium?