Suppose that X is the time it takes a randomly chosen professor in a university department to type and send a standard letter of recommendation for a past student who is applying for a graduate degree program. Suppose X has a normal distribution, and assume the mean is 10.5 minutes and the standard deviation 3 minutes. If you were to take a random sample of 50 professors and measure the time it takes each one of them to type and send such a standard letter of recommendation, what is the probability that their mean time is less than 9.5 minutes?