What Is the Mole Fraction of Methane in a Gaseous

What is the mole fraction of methane in a gaseous mixture that consists of 8.00 g of methane and 12.00 g of ethane (C₂H₆) in a 3.50 L container maintained at 35.20 °C?

A) 0.400
B) 0.434
C) 0.556
D) 0.800
E) 1.50