A software distributor has opened a new customer call center to assist customers with the installation and use of their software. The manager is assuming that the amount of time required to service a customer, X, is a normally distributed random variable. In an attempt to get some information on the population mean service time, , the manager has selected a random sample of 16 calls and found the average service time is 24 minutes withS=4.2 minutes.

The manager would like to take another sample and determine a 95% confidence interval with a margin of error of 1.5 minutes. What sample size would be needed to achieve this goal? A.64 calls B.30 calls C.6 calls D.31 calls