48. A mass-spring system is shown in the figure where the spring constant k = 100 N/m and the mass is 4 kg. Assuming the initial velocity is 3.5 m/s, what is the amplitude of the motion? (A) 0.5 m (B) 0.7 m (C) 0.8 m (D) 0.9 m (E) 1.2 m