The ACT is an exam used by colleges and universities to evaluate undergraduate applicants. The test scores are normally distributed. In a recent year, the mean test score was 21.1 and the standard deviation was 5.3. The test scores of four students selected at random are 15, 22, 9, and 35.
(a) Find the z-scores that corresponds to each value
(b) Determine whether any of the values are unusual.