The mass of a spring-mass system, with \(m=15 \mathrm{~kg}\) and \(k=25 \mathrm{kN} / \mathrm{m}\), vibrates on a horizontal surface under a harmonic force of magnitude \(200 \mathrm{~N}\) and frequency \(20 \mathrm{~Hz}\). Find the resulting amplitude of steady-state vibration. Assume the coefficient of friction between the mass and the horizontal surface as 0.25.