5.36 Alkalinity of river water. The alkalinity level of water specimens collected from the Han River in Seoul, Korea, has a mean of 50 milligrams per liter and a standard deviation of 3.2 milligrams per liter. (Environmental Science & Engineering, Sept. 1, 2000.) Assume the distribution of alkalinity levels is approximately normal and find the probability that a water specimen collected from the river has an alkalinity level a. exceeding 45 milligrams per liter.
b. below 55 milligrams per liter.
c. between 51 and 52 milligrams per liter