Five jobs are waiting for processing through two work centres.Their processing time (in minutes)at each work centre is contained in the table below.Each job requires work centre Sigma before work centre Delta.According to Johnson's rule,what sequence of jobs will minimize the completion time for all jobs?
A)R-S-T-U-V
B)S-V-T-R-U
C)S-U-T-V-R
D)V-R-U-S-T
E)none of the above

Question

Five jobs are waiting for processing through two work centres.Their processing time (in minutes)at each work centre is contained in the table below.Each job requires work centre Sigma before work centre Delta.According to Johnson's rule,what sequence of jobs will minimize the completion time for all jobs? 
A)R-S-T-U-V 
B)S-V-T-R-U 
C)S-U-T-V-R 
D)V-R-U-S-T 
E)none of the above

Quizplus · Accepted Answer

According to Johnson's rule, we need to first identify the operations with the minimum processing time (time taken at both work centres combined) and the maximum processing time.

Minimum processing times:
Job S: 6 minutes (3 + 3)
Job U: 10 minutes (2 + 8)

Maximum processing times:
Job R: 24 minutes (12 + 12)
Job V: 20 minutes (4 + 16)

Based on this, we can arrange the jobs in the following sequence: S-U-T-V-R.

Job S and Job U are performed first since they have the lowest combined processing time. After that, we choose the job that has the lowest processing time at the second work center (Delta) which is T (12 minutes). Next, we choose the remaining jobs based on their processing time at the first work center (Sigma) - Job V (4 minutes) has the lowest processing time, followed by Job R (12 minutes).

Therefore, the correct answer is C) S-U-T-V-R.

Five Jobs Are Waiting for Processing Through Two Work Centres