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.