Cost array [2, 7, 8, 9] → cost per liter of petrol at each petrol pump.
Distance array [0, 15, 45, 80] → distance of each petrol pump from the starting point.
Vehicle mileage = 1 km/litre, meaning 1 litre of petrol covers exactly 1 km.
tank capacity: 70 litre
Goal: Reach 100 km with minimum cost by strategically refueling at petrol pumps.