The waist circumference of males 20-29 years old is approximately normally distributed, with mean 87.5 cm and standard deviation 10.2 cm. (a) Use the normal model to determine the proportion of 20- to 29-year-old males whose waist circumference is less than 100 cm. (b) What is the probability that a randomly selected 20-to 29-year-old male has a waist circumference between 80 and 100 cm? (c) Determine the waist circumferences that represent the middle 90% of all waist circumferences. (d) Determine the waist circumference that is at the 10th percentile.