IMPORTANT NOTE:

 

This material can only be used as a reference. The types of questions and number of questions for the final examinations vary every year. For preparing the final examination, you should go through the materials as described in the classes with the priorities as discussed by Dr. Dai in the last class.

 

 

 

 

SAMPLE FINAL QUESTIONS

 

Instructions:

1.      All answers should be written on question paper provided by circling the correct choice or writing in the spaces provided. You may write on the back of the page if necessary.

2.      Your answers should be written clearly and legibly.

3.      This is a closed book exam. Tables and formulas are provided. You should mention the table you are using to obtain your answer.

4.      Calculations may be done on a separate sheet. However, all sheets used are required to be submitted.

5.      Calculators without programming functions may be used for numerical calculations. Requirements for the use of the calculators are as described in the class.

6.      This examination constitutes 50% of the course grade.

____________________________________________________________________

 

PART A (ANSWER ALL QUESTIONS)

FOR QUESTIONS 1 - 10, STATE WHETHER TRUE OR FALSE:

 

1.                  Waiting line theory provides a means of forecasting arrival and service rates.

2.                  The best way to evaluate a job assignment situation with two machines is Johnson's method.

3.                  It is best to use small alpha values when forecasting a product whose real demand is erratic.

4.                  The bill of materials file contains a complete list of all materials currently on hand and on order.

5.                  The ABC classification  is used to identify components in the product structure tree of an MRP.

6.                  Companies that are called on monthly by vendor's sales representatives tend to use the fixed time period reordering system.

7.                  Assembly lines relate most closely to a process layout.

8.                  Central to the waiting line problem is a trade-off decision - comparing the extra cost of providing more rapid service with the costs of waiting.

9.                  The utilization factor in a waiting line system is the ratio of the service rate and the necessary idle time.

10.              In the EOQ model, the average inventory will always be Q.

 

FOR QUESTIONS 11-15, SELECT THE BEST ALTERNATIVE:

 

11.       Capacity balance can be obtained by:

a. buffer inventories

b. decoupling through backup equipment

c. adding capacity to bottleneck stages

d. all of the above

e. none  of the above.

 

12.       Linear programming is useful principally in problems:

a. which cannot be handled by a computer

b. which can be solved graphically

c. which require simultaneous solutions to many equations

d. which are impossible to solve by other methods.

 

13.       Which of the following is a characteristic of critical path scheduling techniques?

a. The jobs or tasks are dependent on each other.

b. Interruptions may be permitted if they are documented.

c. The jobs or tasks must be well defined, and their completion marks the end of the     project.

d. The jobs or tasks do not necessarily have to be in a predetermined sequence.

 

14.       Fixed order quantity models are:

a. time triggered

b. fixed for a specified time period

c. made up of a variable order size

d. event triggered.

 

15.       The reason for low level coding in MRP is:

a. to show the relative importance of component items

b. to make it easier for the computer to search

c. to show the offset lead times in perspective

d. so that the transaction files can be updated easily.

 

 

16.       In the Lamson case, when your team had a stockout in a given period, did you have to fill or satisfy backorders? What extra information other than the actual sales would have helped you to make better production decisions?

 

PART B (ANSWER ANY 5 QUESTIONS)

 

17.       Fastcomp buys computer chips from a supplier. The cost of a chip is $80 per unit; the company incurs a cost of $1000 per order to process the order. Fastcomp has determined that it costs 12% per year of an item’s cost to hold the item in inventory. The lead time for delivery is 1.5 months. The company uses 120,000 computer chips per year. From historical data, Fastcomp believes the demand during lead time is normally distributed with a mean of 15,000 and a standard deviation of 2000. Determine the economic order quantity and the reorder point for a service level of 98%.

 

18.       Dr. Wu, operations manager at Nesa Electronics, has to develop an assembly line balance for a line assembling electric relays. The firm needs to produce 1400 electric relays per work day. Due to breaks and lunch, there are 420 working minutes in a work day. The following table lists the tasks, precedence relationships, and average task time required to produce a relay.

 

TASK              TIME (sec)                  PRECEDING TASK(S)

A                     13                                            -

B                      4                                              A

C                     10                                            B

D                     10                                            -

E                      6                                              D

F                      12                                            E

G                     5                                              E

H                     6                                              F,G

I                       7                                              H

J                       5                                              H

K                     4                                              I,J

L                      15                                            C,K

 

(a)                Compute the maximum cycle time Nesa can have and still produce 1400 relays per day.

(b)               Compute the theoretical minimum number of work stations required.

(c)                Use the ranked positional weight technique (RPWT) to allocate tasks to work stations that attempts to minimize the number of work stations while producing at least 1400 units per day.

(d)               For the solution in (c), compute the actual cycle time and the actual production rate that would result.

(e)                Compute the efficiency of the line balance in (c).

 

19.       A company manufactures two products A and B using three inputs, labor, material R and material S. To make one unit of product A requires 6 lb. of R, 7.5 lb. S, and 9 person-hours of labor. To make unit of B requires 12 lb. of R, 4.5 lb. of S, and 6 person-hours of labor. The demands for the products are such that the company can sell as much of each product as it can produce and earn a profit of $3 per unit of A and $4 per unit of B.  However, only 900 lb. of R, 675 lb. of S, and 1200 person-hours of labor are available to the company each day.

 

20.       Andy Arthurson is an independent computer software consultant. He has five jobs awaiting completion. Following are the estimated work times required to complete each job and the due dates requested by customers.

 

JOB                 PROCESSING TIME              DUE DATE (DAYS                                                     (DAYS)                       FROM            PRESENT)

 

A                                 12                                            52

B                                  16                                            37

C                                 8                                              28

D                                 20                                            57

E                                  6                                              31

 

(a)    Develop a schedule for the above jobs using shortest processing time rule. Calculate mean flow time and mean lateness for this sequence.

(b)   Develop a schedule using the critical ratio rule.  Calculate mean flow time and mean lateness.

 

21.       Acme Advertising has decided to purchase two fax machines. Two departments, Design and Sales, will be the primary users of the machines. Each department expects to generate 36 documents per eight-hour day that need to be faxed; the timing of these transmissions follows a Poisson distribution. The time it takes to transmit each document is exponentially distributed with an average transmission time of 10 minutes. Each department wants to have its own machine to use exclusively (no other department can use it). The manager of Purchasing wants the two machines to be in a common area that both departments can use.

 

Compare the above two configurations in terms of (a) time in queue, (b) time in system and (c) average number of items waiting in line to be transmitted. Comment on the implications of your results.

 

22.       The diagram below shows a product structure tree for product A.

 

                                                                                    A

                                                                                     |                                 .

                                                 |                                                                      |

                                                B(2)                                                                 C(1)                                                                

             |                                                                      |                      .          

                                     |                      |                                  |                      |                      |

                                    D(3)                 F(1)                             B(3)                 D(1)                 E(4)

                                     |                                                          |                      |

                                     |                                              |                      |          |

                                    E(1)                                         D(3)                 F(1)     E(1)

                                                                                     |

                                                                                    E(1)

 

Additional information about all the items is as follows:

 

                                                                        Scheduled                    Beginning

Item                 Lead time         Lot Size            Receipts                       Inventory

                          (weeks)

  A                          2                     20              10 in wk 3                           5

  B                           2                     40              20 in wk 7                          10

  C                          1                  LFL*                   -                                   -

  D                          3                   160                     -                                100

  E                           2                  LFL              60 in wk 2                        100

  F                           2                  LFL              40 in wk 5                           -

 

(NOTE: * LFL = Lot For Lot)

 

(a)  Draw a Low-Level coded Product Structure Tree.

(b)  If 20 units of A are required in week 10, develop the MRP plan for items A, B, C, and D, using the tabulated format shown below. for the gross requirements, scheduled receipts, on hand from prior period, net requirements, planned order receipt and planned order release.

 

 

1

2

3

4

5

6

7

8

9

10

Gross requirements

 

 

 

 

 

 

 

 

 

 

Scheduled receipts

 

 

 

 

 

 

 

 

 

 

On hand from prior period

 

 

 

 

 

 

 

 

 

 

Net requirements

 

 

 

 

 

 

 

 

 

 

Planned order receipt

 

 

 

 

 

 

 

 

 

 

Planned order release