Problem $2.$ Consider the sewer system shown below. The concentration of dissolved solids in stream A is $50m\frac{g}{L}.$ Stream B has a flow rate of $100\frac{L}{m}in$ and a dissolved solids concentration of $20wt\%($note that $1wt\%$ equals $10\frac{g}{L}).$ The concentration of dissolved solids at manhole $2$ is $1000m\frac{g}{L}.$ What is the flow rate of stream A$?$ Answer $=21,000$ L$/$min$.$