Five jobs are waiting for processing through two work centers.Their processing time (in minutes)at each work center is contained in the table below.Each job requires work center Sigma before work center 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)R-V-T-S-U

Question

Five jobs are waiting for processing through two work centers.Their processing time (in minutes)at each work center is contained in the table below.Each job requires work center Sigma before work center 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)R-V-T-S-U

Quizplus · Accepted Answer

According to Johnson's rule, we need to identify the operation that has the minimum processing time at both work centers. For this, we first find the shortest time at each work center:

Sigma: 10, 8, 6, 5, 7
Delta: 6, 7, 9, 8, 10

The minimum processing time at both work centers are for job S (Sigma: 5, Delta: 7). So, we first process job S, then either job U or job T (both have the same minimum processing time at both work centers: Sigma: 6, Delta: 8), then either job V or job R (both have the same minimum processing time at both work centers: Sigma: 7, Delta: 9), and finally job R or job V (whichever was not processed in the previous step) and job U (Sigma: 11, Delta: 10). Therefore, the sequence that minimizes the completion time for all jobs is S-U-T-V-R.

Five Jobs Are Waiting for Processing Through Two Work Centers