The life spans of a species of fruit fly have a bell-shaped distribution, with a mean of 31 days and a standard deviation of 4 days. (a) The life spans of three randomly selected fruit flies are 32 days, 28 days, and 42 days. Find the z-score that corresponds to each life span. Determine whether any of these life spans are unusual. (b) The life spans of three randomly selected fruit flies are 39 days, 27 days, and 43 days. Using the Empirical Rule, find the percentile that corresponds to each life span. (a) The z-score corresponding a life span of 32 days is (Type an integer or a decimal rounded to two decimal places as needed.)