Liquid Solution

Two liquids ' $A$ ' and ' $B$ ' form an ideal solution. At 300 K , the vapour pressure of a solution containing 1 mole of ' $A$ ' and 3 moles of ' $B$ ' is 550 mm Hg . At the same temperature, if one more mole of ' $B$ ' is added to the solution, the vapour pressure of solution increases to 560 mm Hg . Then the ratio of vapour pressures of $A$ and $B$ in their pure state is