Your body mass index (BMI) is your weight in kilograms divided by the square of your height in meters. Online BMI calculators allow you to enter weight in pounds and height in inches. High BMI is a common but controversial indicator of being overweight or obese. A study by the National Center for Health Statistics found that the BMI of American young women (ages 20 to 29) is approximately Normally distributed with mean 26.8 and standard deviation 7.4.

a. People with BMI less than 18.5 are often classed as “underweight.” What percent of young women are underweight by this criterion?

b. Suppose we select two American young women in this age group at random. Find the probability that at least one of them is classified as underweight.