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6. The mean weight of 700 male students at a certain college is 151 pounds and the standard deviation is 15 pounds. Assuming that the weights are normally distributed, find how many students weigh (a) between 120 and 155 pounds; (b) more than 185 pounds; (c) less than 140 pounds and more than 160 pounds. (d) Find the probability that 4 out of 5 students selected at random weigh between 120 and 155 pounds