Answer
$$M_{C A}=226 \mathrm{~N} \cdot \mathrm{m}
$$
Work Step by Step
$$
\begin{aligned}
&\mathbf{u}_{C A}=\frac{|-2 \mathbf{i}+2 \mathbf{j}|}{\sqrt{(-2)^2+(2)^2}}\\
&\mathbf{u}_{C A}=\{-0.707 \mathbf{i}+0.707 \mathbf{j}\}\\
&M_{C A}=\mathbf{u}_{C A} \cdot\left(\mathbf{r}_{A D} \times \mathbf{F}\right)=\left|\begin{array}{ccc}
-0.707 & 0.707 & 0 \\
2.5 & 0 & 4 \\
50 & -20 & -80
\end{array}\right|\\
&M_{C A}=226 \mathrm{~N} \cdot \mathrm{m}
\end{aligned}
$$
