Many people have answered this question on Chegg but I think they are incorrect. Can someone post answer to this?

At the SuperSpeedy drive-through the time between consecutive customer arrivals has a mean of 50 seconds and a standard deviation of 30 seconds. There are two servers whose service time averages 80 seconds with a standard deviation of 20 seconds. Assume that no customers leave the drive-through after entry. a. What is the utilization of the employees? b. What is the average time a customer spends at the drive-through? What fraction of that is waiting in the queue? c. How many cars on average are in the drive-through lane (including those in service)? d. What suggestions would you have for the drive-through to improve customer satisfaction