Calculation of Heat Vaporization

Question: Methane has a boiling point of -164 °C at 1.0 atm and a vapor pressure of 42.8 atm at -100 °C. What is the heat of vaporization of methane?

I have the final answer for this one but no matter what I calculated, it is not the same answer in the back of the book.

i get 9.24kJ/mol...