Answer
$$
\mathbf{M}_A=\{-16.0 \mathbf{i}-32.1 \mathbf{k}\} \mathrm{N} \cdot \mathrm{m}
$$
Work Step by Step
$$
\begin{aligned}
\mathbf{F} & =100\left(\frac{-0.4 \mathbf{i}+0.6 \mathbf{j}+0.2 \mathbf{k}}{0.7483}\right) \\
\mathbf{F} & =\{-53.5 \mathbf{i}+80.2 \mathbf{j}+26.7 \mathbf{k}\} \mathbf{N} \\
\mathbf{M}_A & =\mathbf{r}_B \times \mathbf{F}=\left|\begin{array}{ccc}
\mathbf{i} & \mathbf{j} & \mathbf{k} \\
0 & -0.6 & 0 \\
-53.5 & 80.2 & 26.7
\end{array}\right|=\{-16.0 \mathbf{i}-32.1 \mathbf{k}\} \mathbf{N} \cdot \mathbf{m}
\end{aligned}
$$
$$
\mathbf{M}_A=\mathbf{r}_C \times \mathbf{F}=\left|\begin{array}{ccc}
\mathbf{i} & \mathbf{j} & \mathbf{k} \\
-0.4 & 0 & 0.2 \\
-53.5 & 80.2 & 26.7
\end{array}\right|=\{-16.0 \mathbf{i}-32.1 \mathbf{k}\} \mathbf{N} \cdot \mathrm{m}
$$
