For the ventilation system shown, the combined resistance of the trunk airways and the shafts is 2.2 Ns$^2$m$^{-8}$. The resistances of splits A and B are 0.5 Ns$^2$m$^{-8}$ and 0.8 Ns$^2$m$^{-8}$ respectively. A regulator of size 2.0 m$^2$ is placed in split A. Considering the fan generates a pressure of 1000 Pa, the air flow in m$^3$/s in split B is ______.