25. assume that the mean hourly cost to operate a commercial airplane follo0ws the normal distribution with a mean of $2,100 per hour and a standard deviation of $250. what is the operating cost for the lowest 3 percent of the airplanes? (show calculations)

31. assume a bionomial proability distribution with n=50 and pi= .25 compute the following (show the calculation)

a) the mean and the standard deviation of the random variable

b) the probability that X is 15 or more

c) the probability that x is 10 or less