A training program designed to upgrade the supervisory skills of production-line supervisors has been offered for the past five years at a Fortune 500 company. Because the program is self-administered, supervisors require different numbers of hours to complete the program. A study of past participants indicates that the mean length of time spent on the program is 500 hours and that this normally distributed random variable has a standard deviation of 100 hours. Suppose the training-program director wants to know the probability that a participant chosen at random would require between 550 and 650 hours to complete the required work. Determine that probability showing your work.