1. After an all-night study session the day before their last final exam, four students decide to stop by for some much – needed coffee at the campus Starbucks. They arrive at 8.30am and are dismayed to find a rather long line. Fortunately for the students, a Starbucks executive happens to be in line directly in front of them. From her, they learn the following facts about his Starbucks location: (I) There are three employees types: ? There is a single cashier who takes all orders, prepares non beverage food items, and grinds coffee, and pours drip coffee. ? There is a single frozen drink maker who prepares blended and iced drinks. ? There is a single espresso drink maker who prepares espressos, lattes and steamed drinks. (II) There are typically four types of customers: ? Drip coffee customers order only drip coffee. This requires 15 seconds of the cashier’s time to pour the coffee. ? Blended and iced drink customers order a drink that requires the use of the blender. These drinks take on an average 90 seconds of work of the frozen drink maker. ? Espresso drink customers order a beverage that uses espresso and/or steamed milk. On an average, these drinks require 60 seconds of work of the espresso drink maker. ? Ground coffee Customers buy one of Starbucks’ many varieties of whole bean coffee and have it ground to the specification at the store. This requires a total of 80 seconds of the cashiers time ( 30 seconds to pour the coffee and 50 seconds to grind the whole bean coffee) (III) The customers arrive uniformly at the following rates from 7 a.m. ( when the store opens) until 10 a.m. ( when the morning rush is over ) with no customers arriving after 10 a.m.: ? Drip coffee customers: 20 per hour? Blended and iced drink customers: 25 per hour? Express Drink customers: 40 per hour? Ground coffee Customers: 10 per hour (IV) Each customer spend on average 20 seconds with the cashier to order and pay. (V) Approximately 25 percent of all customers order food which requires an additional 20 seconds of the cashier’s time per transaction while waiting in line, the students reflect on these facts and they answer the following questions:
2 a. Create a process flow diagram. b. Calculate the capacity (in minutes) at each station (cashier, frozen drinks, espresso). c. Calculate the total workload (in minutes) at each station given the customer arrival rate. d. Calculate the (implied) utilization at each station? e. Which resource has the highest implied utilization? Which station creates the bottleneck?
From their conversation with the executive, the students learn that Starbucks is considering promotion on all scones (half price!), which marketing surveys predict will increase the percentage of the customers ordering food to 30 percent (the overall arrival rates of customers will not change). However the executive is worried about how this will affect the waiting times for customers. f. How do the levels of the implied utilization change as a response to this promotion?