At 20°C Chloroform (Mw 119

At 20°C chloroform (mw 119.38 g/mol) has a vapor pressure of 159 Torr. When 50.0 grams of an unknown compound is mixed with 100.0 grams of chloroform at 20°C the vapor pressure of chloroform over the mixture drops to 69.1 Torr. What is the molecular mass of the added compound?

A) 70.1 g·mol^-1
B) 139 g·mol^-1
C) 77.7 g·mol^-1
D) 45.9 g·mol^-1
E) More information is needed to answer the question