A \(40 \mathrm{~kg}\) block is connected to a spring of stiffness \(1 \times 10^{5} \mathrm{~N} / \mathrm{m}\) and slides on a surface with a coefficient of friction 0.2 . When a harmonic force of frequency \(60 \mathrm{rad} / \mathrm{s}\) is applied to the block, the resulting amplitude of steady-state vibrations is \(3 \mathrm{~mm}\). What is the amplitude of the excitation?