Torque of a force in space

The force $\vec{F}=(10\hat{ı}-5.0\hat{ȷ}+20\hat{k})\mathrm{N}$ is applied at the point with position $\vec{r}=(0.30\hat{ı}+0.40\hat{ȷ})\mathrm{m}$ relative to the pole $O$. Compute the torque of the force about $O$ and its magnitude.