Eighty kilograms (kg) of store material is to be transported to a location 10 km away. Any number of couriers can be used to transport the material can be packed in any number of units of 10, 20 or 40 kg. Courier charges are Rs. 10 per hour. Couriers travel at the speed of 10 km/hr if they are not carrying any load, at 5 km/hr if carrying 10 kg, at 2 km/hr if carrying 20 kg and at 1 km/hr if carrying 40 kg. A courier cannot carry more than 40 kg of load. The minimum cost at which 80 kg of store material can be transported will be

- Rs. 180
- Rs. 160
- Rs. 140
- Rs. 120