Step 1: Vogel’s Approximation Method (VAM)
Given Cost Matrix
Factories → / Warehouses ↓ W1 W2 W3 Supply
F1 4 8 5 20
F2 6 10 7 30
F3 5 9 6 50
Demand 30 40 30
Step 1.1: Calculate Penalties (Row & Column Differences)
Initial Feasible Solution (VAM)
Factories → / Warehouses ↓ W1 W2 W3 Supply
F1 20 0 0 20 → 0
F2 0 30 0 30 → 0
F3 10 10 30 50 → 0
Demand 30 → 0 40 → 0 30 → 0
Initial Cost Calculation
(20×4)+(10×5)+(30×6)+(10×9)+(30×6)=80+50+180+90+180=580(20 \times 4) + (10 \times 5) +
(30 \times 6) + (10 \times 9) + (30 \times 6) = 80 + 50 + 180 + 90 + 180 =
580(20×4)+(10×5)+(30×6)+(10×9)+(30×6)=80+50+180+90+180=580
Initial Cost = $580
Step 2: Stepping Stone Method (Optimality Check)
We check opportunity costs for empty cells.
Check (F1, W2)
Closed loop: (F1 → W1) → (F3 → W1) → (F3 → W2) → (F1 → W2)
Opportunity Cost: 8−4+5−9=08 - 4 + 5 - 9 = 08−4+5−9=0
Check (F1, W3)
Closed loop: (F1 → W1) → (F3 → W1) → (F3 → W3) → (F1 → W3)
Opportunity Cost: 5−4+5−6=05 - 4 + 5 - 6 = 05−4+5−6=0
Check (F2, W1)
Closed loop: (F2 → W2) → (F3 → W2) → (F3 → W1) → (F2 → W1)
Opportunity Cost: 6−9+5−6=−46 - 9 + 5 - 6 = -46−9+5−6=−4
Negative cost (-4), so improvement is required!
Step 3: Improve the Solution
Loop path:
(F2 → W1) (+X),
(F3 → W1) (-X),
(F3 → W2) (+X),
(F2 → W2) (-X)
Minimum allocation: X = min(10, 10) = 10.
New Allocations:
Factories → / Warehouses ↓ W1 W2 W3 Supply
F1 20 0 0 20
F2 10 20 0 30
F3 0 20 30 50
Demand 30 40 30
Step 4: Recalculate Total Cost
(20×4)+(10×6)+(20×9)+(20×6)+(30×6)=80+60+180+120+180=560(20 \times 4) + (10 \times 6) + (20 \
times 9) + (20 \times 6) + (30 \times 6) = 80 + 60 + 180 + 120 + 180 =
560(20×4)+(10×6)+(20×9)+(20×6)+(30×6)=80+60+180+120+180=560
✅ New total cost = $560 ✅