$1$ If the arrival rate for loading trucks is $15$ trucks per hour, what is the mean time between arrivals $($in minutes$)?$

$2$ Assume the service rate for a queue in a truck$-$loading operation is $14$ trucks per hour. What is the average service time $($in minutes$)?$

$3$ The average number in the waiting line divided by the average arrival rate yields what measure of waiting line performance?