half of the volume of petrol & kerosene mixture of ratio 7:5 is converted into mixture of ratio 3:1 by substitution method.while the mixture of ratio 7:5 was formed from the mixture of 7:3 by adding the kerosene in it.If the 240 litres petrol is required in replacement method .what is the total amount of kerosene was added to prepare the mixture of 7:5.
1. 100 litres. 2. 400 litres. 3. 50 litres 4. 200 litres.