QUESTION 1
Multiple-Choice Questions
1. Applichem Why does the Frankfurt plant have low cost, low raw material usage, high labor productivity compared to the Garry plant?
a. Labor in Frankfurt is more productive
b. Raw materials in Frankfurt is cheaper
c. Labor rate in Frankfurt is cheaper
d. Frankfurt plant produces fewer formulations
e. All the above statements are true
2. Applichem: Which of the following statements is/are true (based on the case discussion we had in class)?
I. Plant location optimization model suggested that the plant in Japan should be closed
II. Import duty was not considered to calculate the total cost
III. The Mexico plant has the lowest annual design capacity
a. Only I is true
b. Only II is true
c. Only III is true
d. Both I and II are true
e. Both I and III are true
3. Donner: Assume the following data was given for the set-up time and run time for CNC Drill and Manual Drill.
|
|
Set-up Time (per order)
|
Run Time (per board)
|
|
CNC Drill
|
300
|
1
|
|
Manual Drill
|
30
|
16
|
Which of the following statements is/are true?
I. Choose the CNC drill for order (batch) sizes greater than 18
II. Choose the manual drill for order (batch) sizes greater than 18
III. Choose the CNC drill for order (batch) sizes less than 18
IV. You can choose either CNC drill or manual drill for order (batch) sizes equal to 18
a. Only I
b. Only II
c. II and III
d. I and IV
e. I, II, IV
4. In an Excel worksheet, I typed "=5*Norminv(RAND(), 100, 20)" in 10,000 cells. If I take the average of those 10,000 cells, the average will be very close to:
a. 20
b. 100
c. 200
d. 500
e. None of the above
5. Which of the following statements is true?
a. Make-to-order systems in general offer smaller wait times than make-to-stock systems
b. Customers should not wait if utilization is less than one
c. It is possible that adding capacity to a non-bottleneck resource will increase throughput
d. None of the above statements are true
6. Which of the following statements is true?
a. The bottleneck is always the slowest resource
b. A process can have more than one bottleneck
c. Both of the above statements are true
d. Neither of the above statements are true
7. Trojans coffee employs one worker to make both espresso drinks and to pour drip coffee. On average, an espresso drink takes 4 minutes to make and drip coffee takes 1 minute to pour. The number of customers that order espresso drinks is 6 per hour and the number of customers that order drip coffee is 18 per hour. What is the utilization of the Trojans coffee employee?
a. 130%
b. 100%
c. 70%
d. 30%
e. None of the above
8. At Trojans airport, there is one security checkpoint station that all passengers must pass through after checking in and before boarding their flight. At that station, there is one machine to X-ray luggage. Your data shows that passenger arrival process to the checkpoint are Poisson, and that the time to screen each passenger is a constant 3 minutes. How would you classify this queue?
a. M/D/1
b. M/M/1
c. G/D/1
d. None of the above.
9. Which of the following statements regarding the article "The Psychology of Waiting Lines" is true?
a. The customer's satisfaction with his service is the same as his perception of how well it is delivered
b. Installing mirrors near elevators increased the number of complaints the hotel received about the long elevator waits
c. Improvements near the end of the service encounter are likely to improve customer perception more than improvements near the beginning
d. Two or more of the above statements are true
e. None of the above statements are true
10. There is a DVM office just east of our campus. There are 30 seats in the DMV's driver's license written examination room. Unlike our exam, DMV does not have start/end times for the written exam. License applicants show up randomly, start the exam whenever they are ready, and leave the examination room when they are done. They are allowed to stay as long as they want. One applicant arrives to the examination room in every 5 min. Recent survey shows an applicant spends, on average, 40 minutes in the examination room.
What is the average number of applicants in the examination room?
a. 8 applicants
b. 10 applicants
c. 12 applicants
d. 24 applicants
e. None of the above is true
11. Consider a G/M/1 queue with an average inter-arrival time of 10 min, and average service rate of 15 customer per hour. What is the percentage that there is no body in the system?
a. 20%
b. 40%
c. 60%
d. 80%
e. We cannot calculate it with this information
For questions 12 and 13 (Cookie Business Example):
Recall the cookie business example. To refresh your memory, it takes the operator 6 minutes to mix, and 2 minutes to load. It takes the assembler 1 minute to set the oven, 2 minutes to pack, and 1 minute to collect payment. The oven can bake one dozen cookies at one time, and it takes 9 minutes to bake. After baking, it takes 5 minutes to cool the cookies. There are many trays, and the mixer can mix up to 3 dozen at one time. The company makes many kinds of different cookies, depending on what the customer requests.
12. Assume you replace the existing oven with a newer model. The new oven can still bake one dozen cookies at one time, but it takes only 7 min to bake. Which of the statements is correct?
a. Capacity of the overall system stays the same
b. Capacity of the overall system decreases
c. Oven still is not a bottleneck anymore
d. There are two bottlenecks in the system
e. None of the above is correct
13. Still assume all customers order one dozen cookies and a new oven is installed (with 7 min baking capability.) Assume the operator and her roommate keeps the business open 5 hours each day (instead of 4 in the original question.) What is the new daily capacity? (Assume the system is empty when they start the day.)
a. 32 dozens
b. 34 dozens
c. 35 dozens
d. 37 dozens
e. None of the above
14. Which of the following has the lowest average time in system? (Assuming the average inter-arrival and service times are the same for all the systems)
I. M/M/2
II. M/D/2
III. D/D/2
a. I
b. II
c. III
d. II and III have the same average time in system
e. Cannot be determined with the information given in the question
15. Goal: Alex found NCX-10 and Heat Treat as bottleneck resources. What did he do to increase the capacity these bottlenecks?
a. Dedicate personnel at NCX-10 and Heat Treat even though they are idle much of the time, just don't let machine idle
b. Send out some portion of heat treat parts to vendor in town
c. Found old equipment (that is less efficient) to run in parallel to NCX-10
d. Reduce setup time with new fixtures
e. He did all of above
QUESTION 2
Process Management
South Bay ReLifers refinishes old wood furniture specializing in chairs. Their process for refinishing chairs has 10 workers and 4 stations. The firm works 8 hours per day and 5 days per week. They process two types of chairs-FP-chair (fully processed chair) and SP-chair (semi-processed chair). FP-chairs start at the Stripping station, then go to Priming, then to Painting and finally to Inspection after which they are picked up by the customer. SP-chairs start at the Stripping Station and then go to the Priming station, after that they are picked up by the customer. Where there are multiple workers within a station, each worker works independently on his/her own chair. The below process flow diagram describe the flow of the two products. Assume inventory buffers (not shown in process flow diagram) are allowed between each station. Processing times and worker allocation are given below.
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Station
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Staffing
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Processing time (hours per chair per worker)
|
|
Stripping
|
5
|
4
|
|
Priming
|
2
|
2
|
|
Painting
|
2
|
4
|
|
Inspection
|
1
|
1
|
Suppose South Bay ReLifers just processes one product: FP-Chairs.
a) What are the capacities of each of the 4 stations? Which station is the bottleneck? What is the capacity of South Bay ReLifers in chairs per week? (Assume they start the day with enough inventory at each station to work on, so you can ignore the impact of the first unit)
Suppose South Bay ReLifers processes both the products: FP-Chairs and SP-Chairs. There is demand for 20 FP-Chairs and 20 SP-Chairs per week.
b) What are the utilization of each station?
c) Which station is the bottleneck?
QUESTION 3:
Little's Law
Trojan Health Center is going through a crisis. The wait times have gone up and students have been missing class as a result of long waits. To resolve this issue Trojan Health Center has contacted the Marshall Business School and Dean Ellis has agreed to lend the help of the GSBA 534 students.
On average 20 students enter the Trojan Health Center per hour. The process at Trojan Health Center is as follows. The patients first see a front desk staff member who asks them if they want to be assigned to either a nurse practitioner or a doctor. On average there are 5 students at the front desk waiting or being served. On average 50% of the students choose to be assigned to a nurse practitioner.
If assigned to a nurse practitioner, the total time that the student spends in the system from that point forward (including wait) is on average 15 minutes. If assigned to a doctor, then the students wait until an intern takes their vitals before the doctor can see them. On average there are 15 students that are waiting to be seen or being served by the interns and there are 5 students waiting to be seen or being served by the doctors. (Some triangles have been intentionally deleted from the flowchart below).
a) On average how many minutes do the students spend waiting and being served by the front desk staff?
b) On average how many students are waiting or being served by nurse practitioners?
c) On average how many minutes do the students spend waiting for and being served by the interns? On average how many minutes do the students spend waiting for and being served by the doctors
d) What is the average time that an average student spends in the Health Center? How many students are on average in the Health Center?
QUESTION 4
Waiting Time Management
RentAPhone is a new service company that provides European mobile phones to American visitors in Europe. The company currently has 80 phones available at Charles de Gaulle airport in Paris. There are on average 25 customers per day requesting a phone. These requests arrive following a Poisson process. Customers keep their phones on the average 72 hours and these service times also follow a Poisson process. The store is open 24 hours × 7 days each week
Given that RentAPhone currently does not have a competitor in France providing equally good service, customers are willing to wait for the telephones. Yet, during the waiting period, customers are provided a free calling card. Based on prior experience, RentAPhone found that the company incurred a cost of $1 per hour per waiting customer, independent of day or night. (Hint: Consider each phone as a server)
a) Determine the following quantities for this system: a in hours, p in hours, CVa and CVp? Calculate the utilization.
b) How long does a customer, on average, have to wait for the phone?
c) What are the total monthly (30 days) expenses for telephone cards?
QUESTION 5
Linear Programming
Microbrewers Incorporated makes four beers: Light, Dark, Ale, and Premium. The products require: water, malt, hops, and yeast. Assume the supply of water is free, so that it is the amount of other resources that restricts capacity.
The following table gives the pound of each resource required in the production of 1 gallon of each product, the pounds of each resource available, and the revenue received for 1 gallon of each product.
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Light
|
Dark
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Ale
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Premium
|
|
Available
|
|
Malt
|
1
|
1
|
0
|
3
|
|
50
|
|
Hops
|
2
|
1
|
2
|
1
|
|
150
|
|
Yeast
|
1
|
1
|
1
|
4
|
|
80
|
|
|
|
|
|
|
|
|
Revenue
|
6
|
5
|
3
|
7
|
|
|