A $15-\mathrm{kg}$ undamped absorber tuned to $250 \mathrm{rad} / \mathrm{s}$ is added to a $150-\mathrm{kg}$ machine mounted on a foundation of stiffness $1 \times 10^7 \mathrm{~N} / \mathrm{m}$. At $250 \mathrm{rad} / \mathrm{s}$, the amplitude of the absorber mass is $3.9 \mathrm{~mm}$. What is the amplitude of the machine at $275 \mathrm{rad} / \mathrm{s}$ ?