The manager of the Hippon Drug Store is remodeling his facility and is considering three ways of organizing his branded-items business. The first way is to employ a fast clerk to wait on all customers. Assume such a clerk serves customers exponentially at an average rate of two minutes per customer. The second way is to employ two moderately fast clerks to wait on all customers. Assume each serves customers exponentially at an average rate of four minutes per customer. The third way is to use a self-service system in which each customer waits on himself. Self-service, at an average rate of six minutes, is slower than clerk service. The manager wants to calculate the average number of customers in the store, the average time each spends in the store, and the average time each spends waiting for service, under each way of organizing. Assume that customers arrive completely randomly, one at a time, at the rate of 15 per hour. Calculate the operating characteristics of interest to the manager.