4-. A 4kg mass is connected to a spring with spring stiffness constant of 680N/m. The mass is displaced Born and then released. a. What is the force of the spring and acceleration of the mass when the mass has traveled 1.5 cm from the release point? b. What is the energy in the mass-spring system? c. What is the velocity of the mass at the equilibrium point? d. What is the velocity when the mass has travel ed 1.5cm from the release point