Liquid A and B  from ideal solution over the entire range of composition. At the temperature T, equimolar binary solution of liquids A and B has vapour pressure 40 torr.  At the same temperature, a new solution of A and B having mole fractions X_A and X_B, respectively, has vapour pressure of 20 torr. The value of ${\mathrm{X}}_{\mathrm{A}}/{\mathrm{X}}_{\mathrm{B}}$ in the  new solution is ( given that the vapour pressure of pure liquid A is 10 torr at temperature T )