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 that 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.