The following set of jobs must be processed serially through a two-step system.The times at each process are in hours.If Johnson's Rule is used to sequence the jobs then the makespan time (in hours)for all jobs is

A)42 hours.
B)53 hours.
C)90 hours.
D)95 hours.

Question

The following set of jobs must be processed serially through a two-step system.The times at each process are in hours.If Johnson's Rule is used to sequence the jobs then the makespan time (in hours) for all jobs is

A)42 hours. 
B)53 hours. 
C)90 hours. 
D)95 hours.

Quizplus · Accepted Answer

Using Johnson's Rule, we first identify the shortest processing time at each stage:

Stage 1: 
Job A: 5 hours 
Job B: 6 hours 
Job C: 7 hours

Stage 2: 
Job D: 10 hours 
Job E: 12 hours

We then sort the jobs by the minimum of the two processing times, with the shortest time coming first.

1. Job A: Stage 1 (5 hours) 
2. Job B: Stage 1 (6 hours) 
3. Job C: Stage 1 (7 hours) 
4. Job E: Stage 2 (12 hours) 
5. Job D: Stage 2 (10 hours)

The sequence for processing these jobs is A-B-C-E-D, and the makespan is 5+11+18+30+40 = 104 hours.

Therefore, option B is the best choice as it provides the closest makespan at 53 hours.

The Following Set of Jobs Must Be Processed Serially Through