Answer:
d. It is at most 25 percent.
Explanation:
According to Chebyshev's inequality, for a given number of standard deviations, k, no more than 1/k² can be more than k standard deviations from the mean. In this situation the amount of standard deviations from the mean of the upper and lower bound of salaries are:

For k = 2, applying Chebyshev's inequality:

Therefore, at most 25% of the salaries are less than $68,000 or more than $92,000.