Question

A contractor has ten jobs awaiting processing at a bottleneck workstation. The day the job was received, its processing time and due date are given in the following table. It is now the beginning of day 13.

job	day job was received	job processing time (days)	job due day
A	1	6	41
B	2	10	25
C	7	2	19
D	8	9	31
E	9	1	18

Calculate the average throughput time and, for each job, the number of days overdue using the following priority sequencing rules:

(1) First-come-first-serve

(2) Earliest due date

(3) Shortest processing time

(4) The client waiting for job B has informed the contractor that its due date is now day 33. How will this information affect your choice of priority rule?

Answer 1

First come first serve method= The jobs will be arranged as they come so the sequence will be A-B-C-D-E

	In	Out	Due date	Lateness
A	0	6	41	0
B	6	6+10=16	25	0
C	16	16+2=18	19	0
D	18	18+9=27	31	0
E	27	27+1=28	18	10

Average throughput time = 5/28=0.178

Activity	Overdue
A	0
B	0
C	0
D	0
E	10

2= In the earliest due date, the jobs will be arranged as per their due dates. The jobs with the least due date will be completed first. So the sequence will be

E-C-B-D-A

	In	Out	Due date	Lateness
E	0	1	18	0
C	1	1+2=3	19	0
B	3	3+10=13	25	0
D	13	13+9=22	31	0
A	22	22+6=28	41	0

Average throughput time =5/41 =0.12

Activity	Overdue
A	0
B	0
C	0
D	0
E	0

3= In the shortest processing time, the job with the least processing time will be processed first, so the sequence will be as below=E-C-A-D-B

	In	Out	Due date	Lateness
E	0	1	18	0
C	1	1+2=3	19	0
A	3	3+6=9	41	0
D	9	9+9=18	31	0
B	18	18+10=28	25	3

Average throughput time=5/25 =0.2

Activity	Overdue
A	0
B	0
C	0
D	0
E	3

Answer 4=, In this case, the priority rule of Earliest Due Date will have the changed sequence of the jobs so the new sequence will be=E-C-D-B-A