An accelerometer has a natural frequency of \(80 \mathrm{~Hz}\) and a damping coefficient of \(8.0 \mathrm{~N} \cdot \mathrm{s} / \mathrm{m}\). When attached to a vibrating structure, it measures an amplitude of \(8.0 \mathrm{~m} / \mathrm{s}^{2}\) and a frequency of \(50 \mathrm{~Hz}\). The true acceleration of the structure is \(7.5 \mathrm{~m} / \mathrm{s}^{2}\). Determine the mass and stiffness of the accelerometer.