Micron Electronics makes both desktop and laptop personal computers that they sell directly to customers by phone or over the Internet. In addition to making the computers, Micron provides customer support via a 1-800 number. Recently, the manager of the service department conducted a study of the time customers spent on hold waiting for a Micron representative to become available. The data showed that the distribution of time spent on hold is approximately normally distributed, with a mean of 18 minutes and a standard deviation of 4 minutes.

a. Based on this information, what is the probability that a customer will have to wait more than 11.3 minutes?

b. Considering the data collected in the study, what is the probability that a customer will wait less than 2 minutes?

c. Suppose a customer has complained to the customer service manager that she was on hold for 22 minutes. Based on the data collected in the study, how would you respond to this customer? Do you think that the customer is accurate with her claim?

d. The service manager wants to make sure (for all practical purposes) that no one waits longer than 18 minutes. Determine the standard deviation that would be required to meet this goal