A solution has a 1 :4 mole ratio of pentane to hexane. The vapour pressures of the pure hydrocarbons at $20^{\circ}$C are 440 mm Hg for pentane and 120 mm Hg for hexane. The mole fraction of pentane in the vapour phase would be-

Question

( A ) 0.2
( B ) 0.549
( C ) 0.786
( D ) 0.478