A study of the multiple$-$server food$-$service operation at the Red Birds baseball park shows that the average time between the arrival of a customer at the food$-$service counter and his or her departure with a filled order is $8$ minutes. During the game, customers arrive at the rate of five per minute. The food$-$service operation requires an average of $4$ minutes per customer order.

$($a$)$

What is the service rate per server in terms of customers per minute? $($Round your answer to four decimal places.$)$

min$1$

$($b$)$

What is the average waiting time $($in minutes$)$ in the line prior to placing an order? $($Round your answer to two decimal places.$)$

min

$($c$)$

On average, how many customers are in the food$-$service system? $($Round your answer to two decimal places.$)$