4. A block of mass m = 4.2 kg can slide on a frictionless incline at an angle of :9 = 60. The block is connected to a spring with spring constant k by a string and pulley. The block is initially at rest and the spring is relaxed. (a) If the block has speed 1.7 III/S after sliding of = [122 m along the incline, then what is k? (b) How far has the block slid along the incline when it stops? Hint: use conservation of energy. Take 9 = 9.81 n'lf's2 and show all your work. 3" L