(II) A block of mass $m$ is attached to the end of a spring (spring stiffness constant $k$ ), Fig. 8-35. The mass is given an initial displacement $x_{0}$ from equilibrium, and an initial speed $v_{0}$. Ignoring friction and the mass of the spring, use energy methods to find $(a)$ its maximum speed, and $(b)$ its maximum stretch from equilibrium, in terms of the given quantities.