Liquids A and B form an ideal solution in the entire composition range. At 350 K, the vapor pressure of pure A and pure B are 7 × 103 Pa and 12 × 103 Pa, respectively. The composition of the vapor in equilibrium with a solution containing 40 mole percent of A at this temperature is :
(1) xA = 0.76 ; xB = 0.24
(2) xA = 0.37 ; xB = 0.63
(3) xA = 0.28 ; xB = 0.72
(4) xA = 0.4 ; xB = 0.6