At constant temperature, binary ideal solution is formed by two liquids A and B. At equilibrium, mole-fraction of liquid B is 0.4 and vapour state mole-fraction of B is 0.25. P°B = 40 mm, then at the same temperature, what will be the vapour pressure of pure liquid ‘A’ ?
(a) 80 mm
(b) 60 mm
(c) 40 mm
(d) 50 mm