Vapour pressures of pure liquids 'A' and 'D' at 50°C are 500 mm Hg and 800 mm Hg respectively. The binary solution of 'A' and 'D' boils at 50°C and 700 mm Hg pressure. The mole percentage of 'D' in the solution is:
1
33.33 mole percent
2
66.67 mole percent
3
25.75 mole percent
4
75.25 mole percent