According to the air transport association of america, the average

According to the Air Transport Association of America, the average operating cost of an MD-80 jet airliner is $2,087 per hour. Suppose the operating costs of an MD-80 jet airliner are normally distributed with a standard deviation of $170 per hour.

 

At what operating cost would only 20% of the operating costs be less?

At what operating cost would 65% of the operating costs be more? 

 What operating cost would be more than 85% of operating costs?