150 ml of 30% sulphuric acid was added to approximate 400 ml of 12% sulphuric acid solution. Find the approximate concentration Q of the acid in the mixture?  Choose the correct choice from the following:  A) 1 / 2  B) 1 / 3  C) 1 / 4  D) 1 / 6  E) 1 / 5

Rationale: "do not need any computation 30 % - - - - - - - - - - - 21 % - - - - - - - - - 12 % if volume of both sol . were equal the concentration q would be 21 % = 1 / 5 , but 12 % is more than 3 times only possibility is 1 / 6 d"
Answer: D