Near the surface of the Earth, an ideal spring with spring constant k = 50 N/m is on a frictionless horizontal surface at the base of a frictionless inclined plane as shown in the figure. A block with mass M = 0.6 kg is released from rest a distance d = 1.5 m up the incline plane. If the block slides down and compresses the spring 0.5 m from its equilibrium position before coming to rest, what is the angle µ of the inclined plane relative to the horizontal?