Costco customer service has two service desks, one at each entrance of the store and management considers them as separate entities. Customers arrive at the front entrance desk at an average of one every six minutes, while at the back entrance desk they arrive at an average of one every three minutes. The service rate at each service desk is four minutes per customer.
1.How often (% of time) is each service desk busy?
2.How many customers, on average, are waiting in line at each desk?
3.How much time does a customer spend at each service desk (waiting time plus service time)?