A bank wishing to increase its customer base advertises that it has the fastest service and that virtually all of its customers are served in less...

A bank wishing to increase its customer base advertises that it has the fastest service and that virtually all of its customers are served in less than 11 minutes. A management scientist has studied the service times and concluded that service times are exponentially distributed with a mean of 4.5 minutes. Determine what the bank means when it claims 'virtually all' its customers are served in under 11 minutes. What is the proportion of customers served in under 11 minutes?