Answer
$$
M_C=\{-65.0 \mathbf{i}-37.5 \mathbf{k}\} \mathrm{N} \cdot \mathrm{m}
$$
Work Step by Step
$$
\begin{aligned}
M_C & =80(1.5)=75 \mathrm{~N} \cdot \mathrm{m} \\
M_C & =-75\left(\cos 30^{\circ} \mathbf{i}+\cos 60^{\circ} \mathbf{k}\right) \\
& =\{-65.0 \mathbf{i}-37.5 \mathbf{k}\} \mathrm{N} \cdot \mathrm{m}
\end{aligned}
$$
