The test scores for the boys who received their Australian Tertiary Admission Rank (ATAR) are normally distributed. In a recent year, the mean test score for the boys was 63.75 and the standard deviation was 1.75. The test scores of four boys selected at random are 67.50, 66.50, 61.25, and 63.75.

(a) find the z-score that corresponds to each value and

(b) determine whether any of the values are unusual.