A single-cylinder four-stroke gasoline engine with a mass of 90 kg is mounted on four stiff spring pads, each with a stiffness of 30(10³) kN/m, and is designed to run at 3600 rev/min. The mounting system is equipped with viscous dampers which have a large enough combined viscous damping coefficient c so that the system is critically damped when it is given a vertical displacement and then released while not running. When the engine is running, it fi res every other revolution, causing a periodic vertical displacement modeled by 1.2 cos wt mm with t in seconds. Determine the magnification factor M and the overall damping coefficient c.