14. Pollution Control The EPA limit on the allowable discharge of suspended solids into rivers and streams is 60 milligrams per liter (mg/L) per day. A study of water samples selected from the discharge at a phosphate mine shows that over a long period, the mean daily discharge of suspended solids is 48 mg/L, but day-to-day discharge readings are variable. State inspectors measured the discharge rates of suspended solids for n520 days and found s2 539 (mg/L)2. Find a 90% confidence interval for 2  . Interpret your results.