The oxygen dissolved in water exerts a partial pressure of 20 kPa in the vapour above water. The molar solubility of oxygen in water is __________ $\times$ 10^$-$5 mol dm^$-$3. (Round off to the Nearest Integer).

[Given : Henry's law constant = K_H = 8.0 $\times$ 10⁴ kPa for O₂. Density of water with dissolved oxygen = 1.0 kg dm^$-$3 ]