To improve the operation in the control tower of an airport, air traffic control engineers are assessing the delay due to taxi-out time, which is the duration between pushback and takeoff. suppose that the combined taxi-out and takeoff time for commercial jets is a random variable X with mean of 8.5 minutes and a standard deviation of 2.5 minutes. What is the probability that for 36 jets on a given runway the total taxi-out and takeoff time will be between 275 and 320 minutes?
My attempt is shown below. Any corrections and help would be appreciated!
It looks good. Now you have to find out the values for Φ(−2.066) and Φ(0.933)-by looking in the table of the standard normal distribution. You can use the relation Φ(−2.066)=1−Φ(2.066)