Table J.4
Workstation 1 has five jobs waiting to be processed.It is now time 0,and times are expressed in terms of days.All pertinent data are given in the following table.

-Using the information in Table J.4 and the SPT rule,what is the average days past due?
A)fewer than or equal to 1.0
B)greater than 1.0 but fewer than or equal to 2.0
C)greater than 2.0 but fewer than or equal to 3.0
D)greater than 3.0

Question

Table J.4
Workstation 1 has five jobs waiting to be processed.It is now time 0,and times are expressed in terms of days.All pertinent data are given in the following table.
 
-Using the information in Table J.4 and the SPT rule,what is the average days past due?
A)fewer than or equal to 1.0 
B)greater than 1.0 but fewer than or equal to 2.0 
C)greater than 2.0 but fewer than or equal to 3.0 
D)greater than 3.0

Quizplus · Accepted Answer

Using the SPT rule, we process the shortest job first. 
At time 0, Job 5 has the shortest processing time of 1 day, so we process it first. 
At time 1, Job 3 has the shortest processing time of 2 days, so we process it next. 
At time 3, Job 1 has the shortest processing time of 3 days, so we process it next. 
At time 6, Job 4 has the shortest processing time of 4 days, so we process it next. 
Finally, at time 10, we process Job 2, which has a processing time of 5 days. 
Therefore, Job 2 is past due by 5 days, Job 4 by 6 days, Job 1 by 7 days, Job 3 by 9 days, and Job 5 by 10 days. 
The average days past due is (5+6+7+9+10)/5 = 7.4. 
Since this value is greater than 2.0 but fewer than or equal to 3.0, the answer is C.

Table J.4 Workstation 1 Has Five Jobs Waiting to Be Processed.It Is