A Company's Manufacturing Process Uses 500 Gallons of Water at a Time

Multiple Choice

A company's manufacturing process uses 500 gallons of water at a time. A "scrubbing" machine then removes most of a chemical pollutant before pumping the
Water into a nearby lake. To meet federal regulations the treated water must not contain
More than 80 parts per million (ppm.) of the chemical. The machine's output can be
Described by a normal model with standard deviation 4.2 ppm. The company's lawyers
Insist that not more than 2% of the treated water should be over the limit. To achieve
This, to what mean should the company set the scrubbing machine?

A) 80 ppm.
B) 75 ppm.
C) 71.374 ppm.
D) 88.626 ppm.
E) 69.459 ppm.