There are five jobs in a factory. All these jobs have to go through two workstations for processing. Each job is processed on Workstation #1 and then on Workstation #2. The processing time for each job on each workstation is given below.
$\begin{array} { | l | l | l | }
\hline \text { Job } & \text { Time on Workstation {\#}1(minutes)} & \text {Time on Workstation {\#}2 (minutes) } \
\hline \text { A } & 50 & 50 \
\hline \text { B } & 20 & 8 \
\hline \text { C } & 25 & 50 \
\hline \text { D } & 30 & 12 \
\hline \text { E } & 11 & 22 \
\hline \text { F } & 11 & 19 \
\hline
\end{array}$
Using Johnson's sequencing rule, it can be concluded that the makespan of the sequence is:
A) more than 50 but less than or equal to 100 minutes.
B) more than 100 but less than or equal to 150 minutes.
C) more than 150 but less than or equal to 200 minutes.
D) more than 200 but less than or equal to 250 minutes.

Question

There are five jobs in a factory. All these jobs have to go through two workstations for processing. Each job is processed on Workstation #1 and then on Workstation #2. The processing time for each job on each workstation is given below. 
$\begin{array} { | l | l | l | } 
\hline \text { Job } & \text { Time on Workstation {\#}1(minutes)} & \text {Time on Workstation {\#}2 (minutes) } \
\hline \text { A } & 50 & 50 \
\hline \text { B } & 20 & 8 \
\hline \text { C } & 25 & 50 \
\hline \text { D } & 30 & 12 \
\hline \text { E } & 11 & 22 \
\hline \text { F } & 11 & 19 \
\hline
\end{array}$
Using Johnson's sequencing rule, it can be concluded that the makespan of the sequence is:
A) more than 50 but less than or equal to 100 minutes.
B) more than 100 but less than or equal to 150 minutes.
C) more than 150 but less than or equal to 200 minutes.
D) more than 200 but less than or equal to 250 minutes.

Quizplus · Accepted Answer

Johnson's sequencing rule is a heuristic algorithm used to minimize the makespan (total time) of a set of jobs. This rule involves ordering the jobs according to their processing times on both workstations. The first step is to identify the shortest processing time on either workstation. If this shortest time is on workstation #1, we select the job with the shortest processing time on workstation #1. If this shortest time is on workstation #2, we select the job with the shortest processing time on workstation #2. We alternate between selecting the job with the shortest time on workstation #1 and the job with the shortest time on workstation #2 until all jobs have been sequenced.

Using Johnson's sequencing rule, we get the following order of jobs:
E, F, B, D, C, A

The total processing time for this sequence is:
11 + 19 + 8 + 12 + 50 + 50 = 150

Therefore, the makespan of the sequence is more than 150 but less than or equal to 200 minutes. 
Hence, the correct choice is option C.

There Are Five Jobs in a Factory Using Johnson's Sequencing Rule, It Can Be Concluded That the Have