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| 1 | + |
| 2 | + |
| 3 | + |
| 4 | +## Exercise 2b: Solved Excel Solver |
| 5 | + |
| 6 | +### Problem Statement : |
| 7 | + |
| 8 | +Make the mathematical model and determining the designation and the minimum cost of the process. |
| 9 | + |
| 10 | + |
| 11 | +## **Step 1: Enter the Cost Matrix in Excel** |
| 12 | + |
| 13 | +| | A | B | C | D | E | |
| 14 | +| :-- | :-- | :-- | :-- | :-- | :-- | |
| 15 | +| | | T1 | T2 | T3 | T4 | |
| 16 | +| 2 | | | | | | |
| 17 | +| 3 | A | 5 | 24 | 13 | 7 | |
| 18 | +| 4 | B | 10 | 25 | 3 | 23 | |
| 19 | +| 5 | C | 28 | 9 | 8 | 5 | |
| 20 | +| 6 | D | 10 | 17 | 15 | 3 | |
| 21 | + |
| 22 | + |
| 23 | +--- |
| 24 | + |
| 25 | +## **Step 2: Create the Assignment Matrix** |
| 26 | + |
| 27 | +Next to your cost matrix, create a 4x4 grid for assignments (let’s say in G3:J6). |
| 28 | +Each cell will be a binary variable (0 or 1): |
| 29 | + |
| 30 | +- 1 if the operator is assigned to that task, 0 otherwise. |
| 31 | + |
| 32 | +| | G | H | I | J | |
| 33 | +| :-- | :-- | :-- | :-- | :-- | |
| 34 | +| | T1 | T2 | T3 | T4 | |
| 35 | +| 3 | | | | | |
| 36 | +| 4 | | | | | |
| 37 | +| 5 | | | | | |
| 38 | +| 6 | | | | | |
| 39 | + |
| 40 | + |
| 41 | +--- |
| 42 | + |
| 43 | +## **Step 3: Objective Function (Total Cost)** |
| 44 | + |
| 45 | +In a cell (say, **L2**), calculate the total cost using the SUMPRODUCT function: |
| 46 | + |
| 47 | +```excel |
| 48 | +=SUMPRODUCT(B3:E6, G3:J6) |
| 49 | +``` |
| 50 | + |
| 51 | +This multiplies each cost by its assignment (0 or 1) and sums the result. |
| 52 | + |
| 53 | +--- |
| 54 | + |
| 55 | +## **Step 4: Add Constraints for Solver** |
| 56 | + |
| 57 | +You need to ensure: |
| 58 | + |
| 59 | +- Each worker is assigned to **exactly one** task. |
| 60 | +- Each task is assigned to **exactly one** worker. |
| 61 | + |
| 62 | +**For each row (worker):** |
| 63 | +In K3: `=SUM(G3:J3)` (copy down to K6) |
| 64 | +Set each to **equal 1** in Solver. |
| 65 | + |
| 66 | +**For each column (task):** |
| 67 | +In G7: `=SUM(G3:G6)` (copy right to J7) |
| 68 | +Set each to **equal 1** in Solver. |
| 69 | + |
| 70 | +--- |
| 71 | + |
| 72 | +## **Step 5: Configure Solver** |
| 73 | + |
| 74 | +1. Go to **Data** > **Solver**. |
| 75 | +2. **Set Objective:** |
| 76 | + - Set Objective: `L2` (or wherever your total cost is). |
| 77 | + - To: **Min** |
| 78 | +3. **By Changing Variable Cells:** |
| 79 | + - `G3:J6` (your assignment matrix) |
| 80 | +4. **Add Constraints:** |
| 81 | + - `G3:J6` = binary (use "bin" in Solver) |
| 82 | + - `K3:K6` = 1 (each worker assigned to one task) |
| 83 | + - `G7:J7` = 1 (each task assigned to one worker) |
| 84 | +5. Click **Solve**. |
| 85 | + |
| 86 | +--- |
| 87 | + |
| 88 | +## **Step 6: Interpret the Results** |
| 89 | + |
| 90 | +Solver will fill the assignment matrix with 0s and 1s. |
| 91 | +For each row, the "1" indicates which task that worker is assigned to. |
| 92 | + |
| 93 | +### **Example Solution (Optimal):** |
| 94 | + |
| 95 | +| Worker | Task Assigned | Cost | |
| 96 | +| :-- | :-- | :-- | |
| 97 | +| A | 1 | 5 | |
| 98 | +| B | 3 | 3 | |
| 99 | +| C | 2 | 9 | |
| 100 | +| D | 4 | 3 | |
| 101 | +| **Total** | | **20** | |
| 102 | + |
| 103 | + |
| 104 | +--- |
| 105 | + |
| 106 | +## **Summary Table for README** |
| 107 | + |
| 108 | +| Worker | Task 1 | Task 2 | Task 3 | Task 4 | Assignment | |
| 109 | +| :-- | :-- | :-- | :-- | :-- | :-- | |
| 110 | +| A | 5 | 24 | 13 | 7 | 1 (T1) | |
| 111 | +| B | 10 | 25 | 3 | 23 | 3 (T3) | |
| 112 | +| C | 28 | 9 | 8 | 5 | 2 (T2) | |
| 113 | +| D | 10 | 17 | 15 | 3 | 4 (T4) | |
| 114 | + |
| 115 | +**Minimum total time: 20** |
| 116 | + |
| 117 | +--- |
| 118 | + |
| 119 | +## **Tips** |
| 120 | + |
| 121 | +- Use **conditional formatting** to highlight the "1"s in the assignment matrix for clarity. |
| 122 | +- If Solver is not enabled, go to **File > Options > Add-ins > Solver Add-in**. |
| 123 | + |
| 124 | +--- |
| 125 | + |
| 126 | +**Ready! You have solved the assignment problem step by step in Excel using Solver, ensuring the minimum total cost is 20.** |
| 127 | + |
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