Populate the \(2 \times 2\) mass matrix for the axial element that represents a cylindrical aluminum rod with a diameter of \(10 \mathrm{~mm}\), length of \(100 \mathrm{~mm}\), and density of \(2700 \mathrm{~kg} / \mathrm{m}^{3}\). Substitute the numerical mass values \((\mathrm{kg})\).