The ratio of copper to zinc in an alloy 'A' of 7 kgs is 5 ∶ 2. The ratio of the same metals in that order in another alloy 'B' of 7 kgs is 3 ∶ 4. If 28 kg of alloy is made by mixing A and B in quantities x & y respectively so as to have the ratio of copper and zink in the ratio 1 ∶ 1, then x ∶ y is