Answer
$$
\mathbf{M}_o=\{163 \mathbf{i}-346 \mathbf{j}-360 \mathbf{k} \mid \mathrm{N} \cdot \mathrm{m}
$$
Work Step by Step
The coordinates of point $A$ are $A(0.4,0.5,-0.3) \mathrm{m}$. Thus
$$
\begin{aligned}
\mathbf{r}_{O A} & =\{0.4 \mathbf{i}+0.5 \mathbf{j}-0.3 \mathbf{k}\} \mathbf{m} \\
F & =\mathbf{F u}_F=800\left(\cos 60^{\circ} \mathbf{i}+\cos 120^{\circ} \mathbf{j}+\cos 45^{\circ} \mathbf{k}\right) \\
& =\{400 \mathbf{i}-400 \mathbf{j}+56.5 .69 \mathbf{k}\} \mathrm{N}
\end{aligned}
$$
Moment of $\boldsymbol{F}$ About Point $\boldsymbol{O}$.
$$
\begin{aligned}
\mathbf{M}_O & =\mathbf{r}_{O A} \times \mathbf{F} \\
& =\left|\begin{array}{ccc}
\mathbf{i} & \mathbf{j} & \mathbf{k} \\
0.4 & 0.5 & -0.3 \\
400 & -400 & 565.69
\end{array}\right| \\
& =\{162.84 \mathbf{i}-346.27 \mathbf{j}-360 \mathbf{k}\} \mathbf{N} \cdot \mathrm{m} \\
& =\{163 \mathbf{i}-346 \mathbf{j}-360 \mathbf{k}\} \mathbf{N} \cdot \mathrm{m}
\end{aligned}
$$
