Answer
$$
M_C=45.1 \mathrm{~N} \cdot \mathrm{m}
$$
Work Step by Step
$$
\begin{aligned}
& \mathbf{M}_C=\mathbf{r}_{A B} \times(125 \mathbf{k}) \\
& \mathbf{M}_C=(0.2 \mathbf{i}+0.3 \mathbf{j}) \times(125 \mathbf{k}) \\
& \mathbf{M}_C=\{37.5 \mathbf{i}-25 \mathbf{j}\} \mathrm{N} \cdot \mathrm{m} \\
& M_C=\sqrt{(37.5)^2+(-25)^2}\\&=45.1 \mathrm{~N} \cdot \mathrm{m}
\end{aligned}
$$
