statistics
posted by carolyn .
For the major airlines, 21% of all flights depart at least 15 minutes late with a standard deviation of 5%. Currently, 24% of all American Airlines flights depart at least 15 minutes late. If American wants to be in the top 10% of all major airlines with the FEWEST late departures, to what level must American cut its late departures? (please round your answer to 1 decimal place)

I need this answer.