6.64 Female heights Female heights in North America follow a normal distribution with m = 65 inches and s = 3.5 inches. Find the proportion of females who are

a. under five feet.

b. over six feet.

c. between 60 and 70 inches.

d. Repeat parts a–c for North American males, the heights of whom are normally distributed with m = 70 inches and s = 4 inches.