Figure shows a lamina in x-.y plane. Two axes z and z' pass perpendicular to its plane. A force F acts in the plane of lamina at point P as shown. Which of the following statements is incorrect? (The point P is closer to z'-axis than the z-axis).

The direction of $\overrightarrow{\mathrm{\tau }}$ is given by right handed screw rule.
According to this rule, the direction of $\overrightarrow{\mathrm{\tau }}$ caused by $\overrightarrow{\mathrm{F}}$ about z axis is along $\hat{\mathrm{k}}$.
Again, according to this rule, the direction of $\overrightarrow{{\mathrm{\tau }}^{\text{'}}}$ caused by $\overrightarrow{\mathrm{F}}$ about z'-axis is along -$\hat{\mathrm{k}}$
As $\overrightarrow{\mathrm{\tau } } = \overrightarrow{\mathrm{r}} \times \overrightarrow{\mathrm{F}}$ and P closer z'-axis, therefore, $\overrightarrow{{\tau }^{\text{'}}}$ caused about z' axis is smaller than $\overrightarrow{\mathrm{\tau }}$ .
It is meaningless to add torques about two different axes.