My scooty gives an average of 40 kmpl of petrol. But after recent filling at the new petrol pump, its average dropped to 38 kmpl. I investigated and found out that it was due to adulterated petrol. Petrol pumps add kerosene, which is `2/3` cheaper than petrol, to increase their profits. Kerosene generates excessive smoke and knocking and gives an average of 18 km per 900 ml. If I paid Rs 30 for a litre of petrol, what was the additional amount the pump-owner was making? (a) Rs 1.75 (b) Rs 1.80 (c) Rs 2 (d) Rs 2.30