Heat and Mass Transfer

The Lewis number ($Le$) characterizes fluid flows where there is simultaneous heat and mass transfer. If the thermal diffusivity of air is $\alpha = 2.2 \times 10^{-5}\text{ m}^2/\text{s}$ and the mass diffusivity of water vapor in air is $D_{AB} = 2.2 \times 10^{-5}\text{ m}^2/\text{s}$, calculate the Lewis number ($Le = \alpha / D_{AB}$).