this is for a operations research 2 class if that helps

Question 1:(5 subquestions, 50 points) A fast-food restaurant has one drive-through window. An average of 40 customers per hour arrive at the window. It takes an average of 1 minute to serve a customer. Assume that the interarrival and service times are both exponential, a) [10 points). On the average, how many customers are waiting in the queue? On the average, how long does a customer spend in the restaurant? I b)[10 points). It was estimated that customer dissatisfaction cost was $1 per minute that they stay in the system. What is the total customer dissatisfaction cost per hour? c) (10 points). What fraction of the time are more than 2 cars in the system