8. A lake with a volume of 10106m3 that fed with a stream with a flow rate of 5m3/sec and pollution concentration equal to 10mg/L, another source of pollution fed the lake with the same pollutant at a rate equal to 0.5m3/sec and a concentration equal to 100mg/L. If the steady state concentration of the system is 3.5mg/L and the system is nonconservative find the reaction rate coefficient