A company's manufacturing process employs 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. Because a fine is 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 standard deviation 4.2ppm. What percent of the batches of water discharged exceeds 80 ppm standard?
A. 11.7%
B. 8.83%
C. 1.17%
D. 88.3%