8. A manager of a major bank undertook a survey of customers. She measured the time spent waiting in line of 50 randomly selected customers. The sample mean and standard deviation of the waiting time are 5.79 minutes and 2.86 minutes respectively. (assume the waiting time follows normal distribution) a. Give a point estimate and a 95% confidence interval for the mean waiting time of the bank's customers. b. Suppose the manager wanted the width of the 99% confidence interval for the mean waiting time to be less than 0.5. How many additional customers would have to be selected?