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 $174 per hour. (Round the value of z to 2 decimal places. Round your answers to 2 decimal places.) (a) At what operating cost would only 23% of the operating costs be less? $Entry field with correct answer 1958.44 (b) At what operating cost would 65% of the operating costs be more? $Entry field with correct answer 2019.95 (c) What operating cost would be more than 85% of operating costs ?