When a machine tool is placed directly on a rigid floor, it provides an excitation of the form

\[ F(t)=(4000 \sin 100 t+5100 \sin 150 t) \mathrm{N} \]

to the floor. Determine the natural frequency of the system with an undamped isolator with the minimum possible static deflection such that when the machine is mounted on the isolator the amplitude of the force transmitted to the floor is less than \(3500 \mathrm{~N}\).