A spring is placed in a vertical position with its lower end supported by a horizontal surface. A stone of mass 4.0 kg is rested on the spring and compresses the spring by 0.02 m. The same spring is then placed horizontally and used to launch the stone along the smooth horizontal surface. The spring is compressed by 0.08 m by the stone and then the spring is suddenly released. What is the speed at which the stone leaved the spring?