13. Assume that a randomly selected subject is given a bone density test. Those test scores are normally distributed with a mean of 0 and a standard deviation of 1 a. Draw and shade a graph, then find the probability of a given bone density test score is between 2.55 and 2.00 b. Draw and shade a graph, then find Pm, the 80th percentile. This is the bone density score separating the bottom 80% from the top 20% c. Draw and shade a graph of Zoos, then find the critical value Zoos