Im trying to do my chem homework and I'm stumped. 


  Determine the solubility of $\ce{N2}$ in water exposed to air at 25°C, if the
  atmospheric pressure is 1.2 atm, assume that the mole fraction of
  nitrogen is 0.78 in air and the Henry's Law constant for nitrogen in
  water at this temperature is $6.1 × 10^{-4} M/atm$.



I have the answer, but i want to know how to solve for it. I've been reading through my notes and the book trying to find a reference through which to approach this problem and i have found none. If anyone can guide me in the right direction that would suffice



Question: Results with and without interaction
Answer: Showing both models is fairly common in some disciplines. In those disciplines showing only the model with the interactions can cause confusion, rather than the other way around. So I don't think your client is necessarily wrong.