Definition of torque

A particle is located at \vec{r}=\left(0.54m\right) \hat{i}+\left(-0.36m\right) \hat{j}+\left(0.85m\right) \hat{k}. A constant force of magnitude 2.6N acts on the particle. find the components of the torque about the origin when the force acts in
a) the positive \hat x direction.
b) the negative \hat z direction.