You are planning employees for a bank. You plan for six tellers. Tellers take 15 minutes per customer with a standard deviation of seven minutes. Customers will arrive one every three minutes according to an exponential distribution (recall that the standard deviation is equal to the mean). Every customer who arrives eventually gets serviced.

a. On average, how many customers would be waiting in line?

b. On average, how long would a customer spend in the bank?

c. If a customer arrived, saw the line, and decided not to get in line, that customer has ________.

d. A customer who enters the line but decides to leave the line before getting service is said to have ________.