Alkalinity of 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 and Engineering, September 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.