Concept:For a fixed pack size, cost is: number of packs × time taken per pack × ₹10/hour, where time = distance ÷ carrying speed.Explanation:If packs are 10 kg: number of packs =8, time =510​=2 h, cost =8×2×10=Rs. 160.If packs are 20 kg: number of packs =4, time =210​=5 h, cost =4×5×10=Rs. 200.If packs are 40 kg: number of packs =2, time =110​=10 h, cost =2×10×10=Rs. 200.Minimum cost is Rs. 160.Answer:Rs. 160, i.e., Option B.