The data below represent the service times, x, taken by a sample of 40 randomly bank tellers working at a Bank branch in located in Dandora Service time (x). Number of tellers (f) 2-4. 4 4-6. 17 6-8. 14 8-10 5 Given that the service time random variable follows a normal distribution with a mean and a standard deviation of a) Determine the mean and standard deviation of x using the sample data above (8 Marks) b) From the result in (a) above, Find the following probabilities and interpret the result i. P (X less or equal to 5) ii. P( 3 less or equal to X less or equal to 9)