A man purchases cold-drink for three consecutive years. In the first year, he purchases cold-drink at the rate of ₹ 8.00 per litre, in the second year, at the rate of ₹ 12.00 per litre and in the third year, at ₹ 16.00 per litre. If he purchases cold-drink worth ₹ 2,400 each year, the average price of cold-drink per litre for the three years is: