Assuming E = 160 GPa and G = 100GPa for a material a strain tensor is given as
$\bigl(\begin{smallmatrix} 0.002 & 0.004 &0.006 \\ 0.004 & 0.003 &0 \\ 0.006 & 0 & 0 \end{smallmatrix}\bigr)$
The shear stress $\tau _{xy}$ is
(a) 400 MPa (b) 500 MPa (c) 800 MPa (d) 1000 MPa