Assume that salaries are normally distributed with the 90^th percentile (90% salaries below this amount) at $77,000 and the 80^th percentile at $70,000. Which of the following claims from HR is correct:

a. Average salary is between $55,000 and $56,000

b. Average salary is between $56,000 and $57,000

c. Average salary is between $57,000 and $58,000

d. Average salary is between $58,000 and $59,000

e. Average salary is between $59,000 and $60,000

f. Average salary is between $60,000 and $61,000

g. Nothing can be said about average salary

** I know the answer in B but need additional help understanding. I kept coming up with an answer not listed above.

THANKS IN ADVANCE.