The mean emission of organic pollutants in water is 11.7 million pounds per day in China. Assume that water pollution in China is normally distributed throughout the year with a standard deviation of 2.8 million pounds of organic emissions per day.
a. What is the probability that on any given day the water pollution in China exceeds 15 million pounds per day?
b. What is the probability that on any given day the water pollution in China is between 12 million and 16 million pounds per day?
c. Suppose that one day the water pollution reading was at the 10.75th percentile. What was the pollution level on that day?
d. If 20 days of water pollution readings in China are taken, what is the probability that the mean of this sample is less than 10 million pounds of organic emissions?