c$.$ What is the expected waiting time $($in hours$)$ for the system $(W?$

Waiting time$($in hours$)$

d$.$ What is the expected number of customers in the queue $(L_q)?$

Number of customers$($queue$)$

e$.$ What is the expected waiting time $($in hours$)$ in the queue $(W_q)?$

Waiting time$($queue$)-$ here the question: a M$/$MS system has an arrival rate of $19$ customers per hour. each server has a service rate of $12$ customers per hour.