A damped single-degree-of-freedom system, with parameters \(m=150 \mathrm{~kg}, k=25 \mathrm{kN} / \mathrm{m}\), and \(c=2000 \mathrm{~N}-\mathrm{s} / \mathrm{m}\), is subjected to the harmonic force \(f(t)=100 \cos 20 t \mathrm{~N}\). Find the amplitude and phase angle of the steady-state response of the system using a graphical method.