Somnath  bought two different kinds of oil, one is soya oil and another is olive oil.There are two mixtures of these two oils . In the first mixture the ratio of the soya and olive oil is in  the ratio of 3 : 4 and in the second mixture the ratio of the  soya and olive oil is 5 : 6 . If he mixes these two mixtures and makes a third mixture of 36 litres in which the ratio of the soya oil and olive oil is 4 : 5.  Find the quantity of the second mixture that is needed to make 36 litres of third type of mixture.