4. A spring is stretched by 4 in by a mass weighing 12lb. The mass is attached to a dashpot mechanism that has a damping constant of 0.3 lb⋅s/ft and is acted on by an external force of 3cos⁡(4t)lb. Determine the steady state response of this system. Use 32ft/s2 as the acceleration due to gravity. What is U(t) in ft?

4. A spring is stretched by 4 in by a mass weighing 12lb. The mass is attached to a dashpot mechanism that has a damping constant of 0.3 lb⋅s/ft and is acted on by an external force of 3cos⁡(4t)lb. Determine the steady state response of this system. Use 32ft/s2 as the acceleration due to gravity. What is U(t) in ft?