Workers in a factory have to take their work to the quality control department before the product reaches the end of the production process. There are a large number of employees and arrivals are...

Workers in a factory have to take their work to the quality control department before the product reaches the end of the production process. There are a large number of employees and arrivals are approximately 20 per hour, following a Poisson process. The time to inspect a part follows an exponential distribution of mean 4 minutes. Calculate the average number of workers in quality control if there are: a. 2 inspectors b. 3 inspectors