In: Operations Management
Question 3
The Operations Manager of a construction company wants to assign four contractors to four jobs in such a way as to minimize the time taken to complete four buildings of a special kind and size. Based on experience, the times taken (in months) for each contractor to complete each job are given in the table below.
.
Jobs | Contractor |
1 2 3 4 | |
1 | 15 15 16 14 |
2 | 20 18 16 19 |
3 | 24 26 20 23 |
4 | 30 35 38 25 |
b. Write an LP formulation that could be used to solve this problem with the relevant LP software packages. [13 marks]
Let assune Xij reprsent the Jobs assignment to the contractor, where i = 1, 2, 3, 4 and j= 1,2,3,4.
Decision Variable - To find the value of Xij to minimize the time to complete the task.
Objective = Min. Z= 15X11+15X12+16X13+14X14+20X21+18X22+16X23+19X24+ 24X31+26X32+20X33+23X34+ 30X41+35X42+38X43+25X44
Constraints -
X11+X12+X13+X14=1
X21+X22+X23+X24=1
X31+X32+X33+X34=1
X41+X42+X43+X44=1
X11+X21+X31+X41=1
X12+X22+X32+X42=1
X13+X23+X33+X43=1
X14+X24+X34+X44=1
Xij = Binary (0 or 1)
Below is the screenshotof the LP table in excel -
Below is the screenshot of the formula applied -
Below is the screenshot of the solver -
Below is the screenshot of the result -