The unbalance of the rotor of a 180-kg motor is equivalent to a mass of 85 g located 150 mm from the axis of rotation. The pad which is placed between the motor and the foundation is equivalent to a spring of constant k = 7.5kN/m in parallel with a dashpot of constant c. Knowing that the magnitude of the maximum acceleration of the motor is 9 mm/s2 at a speed of 100 rpm, determine the damping factor c/cc.