Question

The table below contains information about five jobs waiting to be processed at work center.

Job	Processing Time (Days.)	Days Until Due
a	14	15
b	10	20
c	18	18
d	2	16
e	4	21

a. The sequence that would result using the FCFS rule is:

1. e-b-c-d-a
2. c-a-b-e-d
3. a-b-c-d-e
4. d-e-b-a-c
5. e-d-b-a-c

     

b. The sequence that would result using the SPT rule is:

1. e-b-c-d-a
2. c-a-b-e-d
3. a-d-c-e-b
4. d-e-b-a-c
5. e-d-b-a-c

      

c. The average flow time (completion time) using the SPT rule is

A. 9.6

B. 14

C.16.6

D.18

E. None of the above

d. The average days late using the SPT rule is

A. 9.6

B. 18

C.16.6

D.31.6

E. None of the above

e. The average flow time using the EDD rule is

A. 9.6

B. 18

C.16.6

D.31.2

E. None of the above

f. The average days late using the EDD rule is

A. 9.6

B. 18

C.16.6

D.31.6

E. 13.4

Answer 1

1. C. A-B-C-D-E

2. D. D-E-B-A-C

3. E. NONE OF THE ABOVE(ANSWER IS 20.4)

4. E. NONE OF THE ABOVE(ANSWER IS 9)

5. D. 31.2

6. E. 13.4

FCFS

JOB	PROCESSING TIME	DUE TIME	FLOW TIME	JOB LATENESS
A	14	15	0 + 14 = 14
B	10	20	14 + 10 = 24	4
C	18	18	24 + 18 = 42	24
D	2	16	42 + 2 = 44	28
E	4	21	44 + 4 = 48	27

TOTAL FLOW TIME = 14 + 24 + 42 + 44 + 48 = 172

AVERAGE COMPLETION TIME = FLOW TIME / N = 172 / 5 = 34.4

AVERAGE JOB LATENESS = TOTAL JOB LATENESS / N = 83 / 5 = 16.6

SPT

JOB	PROCESSING TIME	DUE TIME	FLOW TIME	JOB LATENESS
D	2	16	0 + 2 = 2
E	4	21	2 + 4 = 6
B	10	20	6 + 10 = 16
A	14	15	16 + 14 = 30	15
C	18	18	30 + 18 = 48	30

TOTAL FLOW TIME = 2 + 6 + 16 + 30 + 48 = 102

AVERAGE COMPLETION TIME = FLOW TIME / N = 102 / 5 = 20.4

AVERAGE JOB LATENESS = TOTAL JOB LATENESS / N = 45 / 5 = 9

EDD

JOB	PROCESSING TIME	DUE TIME	FLOW TIME	JOB LATENESS
A	14	15	0 + 14 = 14
D	2	16	14 + 2 = 16	0
C	18	18	16 + 18 = 34	16
B	10	20	34 + 10 = 44	24
E	4	21	44 + 4 = 48	27

TOTAL FLOW TIME = 14 + 16 + 34 + 44 + 48 = 156

AVERAGE COMPLETION TIME = FLOW TIME / N = 156 / 5 = 31.2

AVERAGE JOB LATENESS = TOTAL JOB LATENESS / N = 67 / 5 = 13.4

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