Waiting Line Analysis Problem $-$ Single$-$Server Model $/$ Model A

$($There are $5$ questions associated with this problem, one question per page$)$:

The new$-$accounts officer at the Citizens Northern Savings Bank enrolls all new customers in checking accounts. During the three$-$week period in August encompassing the beginning of the new school year at State University, the bank opens a lot of new accounts for students. The bank estimates that the arrival rate during this period will be Poisson distributed with an average of four customers per hour. The service time is exponentially distributed with an average of $12$ minutes per customer to set up a new account. The bank wants to determine the operating characteristics for this system to determine if the current person is sufficient to handle the increased traffic.

Question $28(2$ points$)$

Please calculate:

$1)$ Probability of no customers in the system