. A pond receives urban runoff from a stormwater collection and equalization system. The system discharges water to the pond at a steady rate of 2 L/s. The stormwater contains two pollutants of interest: chloride (Cl- ) at a concentration of 500 mg/L and ammonium (NH4 ) at a concentration of 2 mg/L. Chloride is conservative, but ammonium degrades in the pond with a pseudo-first-order reaction rate constant of 0.05 day-1 . The pond also receives water (at a steady rate of Q) from a pristine stream with negligible concentrations of Cl- and NH4 . The pond is well-mixed and is equipped with an effluent weir that keeps its volume at a constant 10,000 m3 . The concentration of chloride in stream effluent stream is 100 mg/L. a. What is the concentration of NH4 (in mg/L) in this stream