The air in the lab is clean before students started their experiments at $10$ a$.$m$.$ Students started their lab experiments at $11$ a$.$m at this time pollutant start to be submitted into the air with reaction rate equal to $\frac{0\mathrm{.}4}{h}r$ at a constant rate of $140m\frac{g}{h}r.$ The lab volume is $500m3$ and fresh air entering the lab at rate equal to $1000\frac{m^3}{h}r.$ Estimate the time for the concentration to reach $0\mathrm{.}1m\frac{g}{m^3}?$