Let x denote the systolic blood pressure of an individual selected at random from a certain population.

Suppose that the normal distribution with mean m 5 120 mm Hg and standard deviation s 5 10 mm Hg is a reasonable model for describing the population distribution of x. (The article “Oral Contraceptives, Pregnancy, and Blood Pressure,” Journal of the American Medical Association [1972]: 1507–1510, reported on the results of a large study in which a sample histogram of blood pressures among women of similar ages was found to be well approximated by a normal curve.)

a. Calculate P(110 , x , 140). How does this compare to P(110 # x # 140), and why?

b. Calculate P(x , 75).

c. Calculate P(x , 95 or x . 145), the probability that x is more than 2.5 standard deviations from its mean value.