Pay special attention to the units for the calculation. In SI, the unit of power is the watt, and $1 \mathrm{W}=1 \mathrm{N}-\mathrm{m}/\mathrm{s}$. Therefore, $40 \mathrm{kW}$ of power is $40,000 \mathrm{N}-\mathrm{m}/\mathrm{s}$.

The rotational speed in $\mathrm{rpm}$ must be converted to units of radians per second. Recall that radians is a dimensionless quantity.

$\mathrm{P}=\mathrm{T\omega }$

$$\begin{gathered} \therefore \mathrm{T}=\frac{\mathrm{P}}{\mathrm{\omega }}=\frac{(40,000 \mathrm{N}-\mathrm{m}/\mathrm{s})}{(900 \mathrm{rev}/\min )(2\mathrm{\pi } \mathrm{rad}/\mathrm{rev})(1 \min /60 \mathrm{s})} \\ =\frac{(40,000 \mathrm{N}-\mathrm{m}/\mathrm{s})}{(94.248 \mathrm{rad}/\mathrm{s})} \\ =424.413 \mathrm{N}-\mathrm{m} \end{gathered}$$