A \(20 \mathrm{~kg}\) block is connected to a spring of stiffness \(1 \times 10^{5} \mathrm{~N} / \mathrm{m}\) and placed on a surface which makes an angle of \(30^{\circ}\) with the horizontal. A force of \(300 \sin 80 t \mathrm{~N}\) is applied to the block. The steady-state amplitude is measured as \(10.6 \mathrm{~mm}\). What is the coefficient of friction between the block and the surface?