SteinMart has seven cashier stations placed strategically around their store so that each of them serves a seventh of the 100 customers that the store sees, on average, per hour. Assume that the inter-arrival times of the customers are exponentially distributed. A cashier takes an average of 3 minutes to serve a customer, but the processing time is highly random with a standard deviation of about 7.5 minutes.
a) For a typical cashier, compute the percentage of time he/she is idle.
b) What is the average number of customers waiting at each of the cashier stations?