The vapor pressure of pure liquid A and B are 70 mm and 90 mm Hg, respectively, at 25°C. The mole fraction of A in a solution (0.3 A and 0.7 B) forms an ideal solution. Calculate the partial pressure of A.
a) 63 mm Hg
b) 66 mm Hg
c) 69 mm Hg
d) 72 mm Hg