4. An object of mass 0.2 kg is hung from a spring whose spring constant is 80 N/m. The object is subject to a resistive force given by -by, where v is its velocity in meters per second. a. Set up the differential equation of motion for free oscillations of the system. b. If the damped frequency is 0.995 of the undamped frequency (when b = 0), what is the value of the constant b? c. What is the Q of the system, and by what factor is the amplitude of the oscillation reduced after 10 complete cycles?