8. If the permutation matrix R is given by

$$

\begin{bmatrix}

0 & 1 & 0 \\

1 & 0 & 0 \\

0 & 0 & 1

\end{bmatrix}

$$, show that R'AR is a P-matrix, where A is given in Prob. 6. This illustrates (4)

of Theorem 11.2.2.