The duration to deliver letter in Selangor area is normally distributed with a mean 5 minutes and standard deviation 2 minutes. Estimate the probability that duration takes a. Longer than 9.5 minutes b. Less than 1.8 minutes c. Between 2.4 and 7.8 minutes. X~N(125,9). Find: a. P(X> 128) b. P(XCOM a. P (Z a) = 0.9920 sivab bisba d. P(Z> a) = 0.3300 Most of the degree programmes at Unisel took average of 132 credit hours with standard deviation of 3 hours. Determine a. the probability that certain programmes have the same credit hours. b. the probability that certain programmes less than 126 hours c. the probability that certain programmes is between 129 and 138 hours