A 2.30 kg cube rests upon a frictionless, horizontal surface. The cube is attached to a horizontal spring (of force constant k = 460 N/m) whose other end is anchored to a nearby wall. The cube is pulled until it lies a distance x;: 4.35 cm from its equilibrium position (x = 0). The cube is then released and undergoes simple harmonic motion. = k wwww x=0 m x = x; (a) Calculate how much work must be done (in J) to stretch the spring from equilibrium (x = 0) to the pre-release position (x;). J (b) with what speed (in m/s) does the cube pass through the equilibrium position once it has been released from x;? m/s