Cerebral blood flow (CBF) in the brains of healthy people is normally distributed with a mean of

Question:

Cerebral blood flow (CBF) in the brains of healthy people is normally distributed with a mean of 74 and a standard deviation of 16.
a. What proportion of healthy people will have CBF readings between 60 and 80?
b. What proportion of healthy people will have CBF readings above 100?
c. If a person has a CBF reading below 40, he is classified as at risk for a stroke. What proportion of healthy people will mistakenly be diagnosed as "at risk"?