Consider the Following to Answer the Question(s) Below

question 9

Multiple Choice

Consider the following to answer the question(s) below:
A company's manufacturing process uses 500 litres 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. Because there is a fine charged if regulations are not met, the company sets the machine to attain an average of 75 ppm in the treated water. The machine's output can be described by a Normal model with a standard deviation 4.2 ppm.
-The company's lawyers insist that not more than 2% of the treated water should be over the limit. In order to achieve this, to what mean should the company set the scrubbing machine? Assume the standard deviation does not change.

• A) 75 ppm
• B) 78.626 ppm
• C) 71.373 ppm
• D) 80 ppm
• E) 60 ppm