(b)
$\left| \begin{matrix}
a - b & b - c & c - a \\
x - y & y - \mathcal{z} & \mathcal{z -}x \\
p - q & p - r & r - p
\end{matrix} \right| = \left| \begin{matrix}
0 & b - c & c - a \\
0 & y - \mathcal{z} & \mathcal{z -}x \\
0 & q - r & r - p
\end{matrix} \right| = 0$ ${(C}_{1} \rightarrow C_{1} + C_{2} + C_{3})$