At Starbucks, customers first order and pay for their drink, and then wait for their drink to be made. There is one cashier and two drinkmakers. Suppose 30 customers arrive per hour to a particular Starbucks, the average time the cashier spends taking an order is 1 minute, and the average time a drinkmaker need to make one customers drink is 3 minutes. On average, 1 customer is waiting to order and pay for his drink, and 5 customers are waiting for their drink to be made. Suppose one customer orders one drink.
a. How long does an average customer spend from the time he enters the Starbucks to the time he receives his drink?
b. What percentage of time is the cashier busy and what percentage of time are the drink-makers busy? If these percentages are less than 1, explain why customers are waiting.
c. What is the maximum number of customers the store can serve per hour?