A machine of mass 400 kg operates at 1500 rpm and has an unbalanced which causes a harmonic repeated force pf magnitude 20,000 N. Design an isolation system to limit the transmitted force to 3,500 N and the amplitude of vibration during operation to 1mm, and the amplitude of vibration during start-up to 10mm. Specify the required stiffness of the isolator and the minimum mass that should be added to the machine. Assume a damping ratio of 0.05.