In a recent year, the ACT scores for the reading portion of the test were normally distributed, with a mean of 21.3 and a standard deviation of 6.2. Find the probability that a randomly selected high school student who took the reading portion of the ACT has a score that is (a) less than 15, (b) between 18 and 25, and (c) more than 34, and (d) identify any unusual events. Explain your reasoning