WOW the HARDEST one YET!!! - Can someone help out?

[jonbon34]

A gaseous hydrocarbon reacts completely with oxygen gas to form carbon dioxide and water vapor. Given the following data, determine ∆Hºf for the hydrocarbon:

∆Hºrxn = -2044.5 kJ/mol hydrocarbon
∆Hºf (CO₂) = -393.5 kJ/mol
∆Hºf (H₂O) = -242 kJ/mol

Density of CO₂ and H₂O product mixture at 1.00 atm, 200 ºC is 0.751 g/L.

The density of the hydrocarbon is less than the density of Kr at the same conditions.