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 find the processing times for each job in the first and second steps:

Job  | First Step | Second Step
---- | ----------| -----------
A    | 2         | 4
B    | 4         | 6
C    | 3         | 7
D    | 5         | 9

Next, we identify the shortest processing time at each step and make a sequence based on that:

Step 2: A
Step 1: C
Step 1: B
Step 2: D

This gives us a total makespan of 53 hours, which is the minimum possible using Johnson's Rule. Therefore, the best choice is B.

The Following Set of Jobs Must Be Processed Serially Through