NEET 2005 Chemistry question

A solution has a 1 : 4 mole ratio of pentane to hexane. The vapour pressure of the pure hydrocarbons at 20°C are 440 mm of Hg for pentane and 120 mm of Hg for hexane. The mole fraction of pentane in the vapour phase would be :

• (A)0.178
• (B)0.278
• (C)0.378
• (D)0.478Correct