Example $2-5$: A storm sewer carries snowmelt containing $1\mathrm{.}200\frac{g}{L}$ of NaCl into a small stream. The stream

has a naturally occurring NaCl concentration of $20m\frac{g}{L}.$ If storm sewer flows at $2000\frac{L}{m}in$ and the

stream flow rate is $2\frac{m^3}{s},$ what is the concentration of salt in the stream after the discharge point? Assume

both flows are completely mixed, that the salt is a conservative substance, and the system is at steady state.