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2. Because of approaching holiday season Omaha\'s Meats is scheduled to work sev

ID: 331986 • Letter: 2

Question

2. Because of approaching holiday season Omaha's Meats is scheduled to work seven days a weelk for the next two months. November's work for Omaha's Meats consists five orders A,B,C,D, and E. Order A takes 5 days to complete and due on day 10, order B takes 10 days and due on day 15, C takes 2 days and due on day 5, order D takes 8 days and due on day 12 and finally order E takes 6 days to process which is due on day 8. Answer the questions below. a. How many possible sequences of these jobs can have for processing? b. Form a table of processing times and due dates. Sequence the jobs with First Come First Served rule. Determine the completion time and tardiness for each job. c. d. Sequence the jobs with Earliest Due Date rule. Determine the completion time and tardiness for each job. Sequence the jobs with minimum slack rule. Determine the completion time and tardiness for each job. e. f. Sequence the jobs with Shortest Processing Time rule. Determine the completion time and tardiness for each job. What sequencing rule would you recommend for Omaha's Meats for average completion time objective? g. h. What sequencing rule would you recommend for Omaha's Meats for minimizing the maximum tardiness objective?

Explanation / Answer

a. Five jobs are required to be sequenced, possible number of sequences = n! = 5! = 120 ways

b. Assume the orders are received in following sequence:

Task

Processing time

Due Date

A

5

10

B

10

15

C

2

5

D

8

12

E

6

8

c. First come first served rule:

Sequence jobs as per received order sequence

Sequence

Job

Processing time

Work Begins

Flow Time

Job Due date

Job Lateness
(Tardiness)

pi

di

1

A

5

0

5

10

-5

2

B

10

5

15

15

0

3

C

2

15

17

5

12

4

D

8

17

25

12

13

5

E

6

25

31

8

54

Completion time = 62 days

d. Earliest due date:

Sequence jobs from early due date to latest due date

Sequence

Job

Process time

Due date

1

C

2

5

2

E

6

8

3

A

5

10

4

D

8

12

5

B

10

15

Job Sequence

Processing time

Work Begins

Flow Time

Job Due date

Job Lateness
(Tardiness)

Job

pi

Di

C

2

0

2

5

-3

E

6

2

8

8

0

A

5

8

13

10

3

D

8

13

21

12

9

B

10

21

31

15

16

e.

Minimum Slack Rule:

Slack = Due date – processing time

Sequence job from lowest slack to highest slack

Job

Process time

Due date

Slack

= Due date – processing time

E

6

8

2

C

2

5

3

D

8

12

4

A

5

10

5

B

10

15

5

Job Sequence

Processing time

Work Begins

Flow Time

Job Due date

Job Lateness
(Tardiness)

Job

pi

Di

E

6

0

6

8

-2

C

2

6

8

5

3

D

8

8

16

12

4

A

5

16

21

10

11

B

10

21

31

15

16

f. Shortest processing time:

Sequence is as follows: Sequence job from shortest processing time to longest processing time

Job

Process time

Due date

C

2

5

A

5

10

E

6

8

D

8

12

B

10

15

Job Sequence

Processing time

Work Begins

Flow Time

Job Due date

Job Lateness
(Tardiness)

Job

pi

di

C

2

0

2

5

-3

A

5

2

7

10

-3

E

6

7

13

8

5

D

8

13

21

12

9

B

10

21

31

15

16

Task

Processing time

Due Date

A

5

10

B

10

15

C

2

5

D

8

12

E

6

8