A pickle-packing plant produces and discharges a waste brine solution with a salinity of 13,000 mg/L NaCl, at a rate of 400 L/min, discharged into a stream with a flow rate above the discharge of 5 million L/d and a salinity of 20 mg/L. Below the discharge point is a prime sport fishing spot, and the fish are intolerant to salt concentrations above 200 mg/L, What must the level of salt in the effluent be to reduce the level in the stream to 200 mg/L?