The z-score of a data is calculated through the equation,
z-score = (x - m)/d
where x is the given value, m is the mean, and d is the standard deviation. Substituting the known values,
z-score = (28,000 - 34000) / 4,000
z-score = -1.5
Thus, the z-score of the 28,000 is -1.5.
