What would be the volumetric strain $\varepsilon_{vol}$, for a shale rock with $E = 4 \times 10^6$ psi and $ u = 0.2$, when subjected to an isotropic change of stress $\sigma_{iso} =$ 3,000 psi? Write the full (3D) acting stress tensors and resulting strain tensor as matrices 3 $\times$ 3