Take a still atmosphere of helium and nitrogen, mixed but each acting as an ideal gas on its own, at a uniform $250\ \text{K}$, with $g = 9.8\ \text{m/s}^2$ at every height. The molar masses are $4.0 \times 10^{-3}\ \text{kg/mol}$ and $2.8 \times 10^{-2}\ \text{kg/mol}$, and $R = 8.314\ \text{J/(mol K)}$. The ratio of the number of helium atoms to nitrogen molecules per unit volume is measured at the ground and at a height of $10\ \text{km}$. How does the ratio at that height compare with the ratio at the ground?