The three-dimensional state of stress at a point is given by
\[
\sigma=\left(\begin{array}{ccc}
10 & 0 & 0 \\
0 & 40 & 0 \\
0 & 0 & 0
\end{array}\right) \mathrm{MPa} .
\]
The maximum shear stress at the point is
- $20 \mathrm{MPa}$
- $15 \mathrm{MPa}$
- $5 \mathrm{MPa}$
- $25 \mathrm{MPa}$