2. In the winter, a stream flows at 10 m/s and receives discharge from a pipe that contains runoff from a nearby road. The pipe has a flow of 5

m³/s. The stream's chloride concentration just upstream of the pipe discharge is 12 mg/L. The maximum concentration (mg/L) that can be discharged through the road runoff pipe without exceeding water quality standards of 20 mg/L in the stream at the mixing point is closest to? a) 21 mg/L b) 28 mg/L c) 36 mg/L d) 42 mg/L e) 56 mg/L