Response to the following problem:
Soup Herman is a restaurant that serves soup and salad. Customers first line up in a cash register line to pay for their meals. After paying, they proceed to one of four salad bars. While all customers purchase salad, only 60% of customers go on to take the soup from one of the two soup stations. During the hours between 6:15 and 8:00 P.M., an average of 140 customers arrive at the restaurant. Assume that the arrival process can be modeled by a Poisson distribution. The time it takes to pay the cashier, get salad, and get soup each follows an exponential probability distribution.
If the cashier takes an average of 40 seconds to collect money from a customer, and the customer averages two minutes to get a salad and one minute to get soup, determine the average time a customer spends paying for and getting food if;
(i) the customer is getting salad only; and
(ii) the customer is getting both soup and salad.