A supermarket has a checkout counter by hiring a full -time cashier. Customers arrive randomly at the counter at an average rate of 20 people per hour. Exponentially distributed service time distribution, with a mean of 2 minutes. This situation has resulted in sometimes long waiting lines and getting complaints from customers. Therefore, managers are considering an alternative to hiring another assistant to stuff groceries into plastic bags. The assistant is expected to reduce the mean time at the counter to 1.5 minutes. Managers want to lower the percentage that more than two customers are at the checkout counter to less than 25%.

a) State the Kendall model/notation for the current operation and determine the values of and

b) Use the model and values obtained in (a) to obtain the values of L, W, Wq and Lq.

c) State the model for the alternative operation and determine the values of and . d) Use the model and the values obtained in (c) to obtain the values of L, W, Wq and Lq.

e) What is the probability that there are more than two customers at the payment counter for models (a) and (c)?

f) Which model is more suitable to use based on (e)?