A block of mass \(M\) is attached to an ideal horizontal spring of spring constant \(k\) and rests on a frictionless horizontal surface at the spring's equilibrium position. A piece of clay of mass \(m\) travels horizontally with speed \(v_0\) toward the block and sticks to it during an impact of negligible duration. Which of the following expressions represents the amplitude of the resulting oscillations of the clay-block-spring system?