Sodium oxide reacts with water to produce sodium hydroxide. 20.0 g of sodium oxide is dissolved in 500 mL of water. Neglecting the change in volume, the concentration of the resulting NaOH solution is $\_\_\_\_$ $\times 10^{-1} \mathrm{M}$.
(Nearest integer)
[Atomic mass: $\mathrm{Na}=23.0, \mathrm{O}=16.0, \mathrm{H}=1.0$ ]
