Answer this multiple choice question: A single server queuing system has an average service time of $16$ minutes per customer, which is exponentially distributed. The manager is thinking of converting to a system with a constant service time of $16$ minutes. The average arrival rate will remain the same. The effect will be to:

$($a$)$decrease utilization.

$($b$)$ increase utilization.

$($c$)$ decrease the average waiting time.

$($d$)$ increase the average waiting time.

$($e$)$ not have any effect since the service time is unchanged.