Homogeneous reactors help

Hi, I am struggling with a homogeneous reactors question and would much appreciate any help! the question I have attached as a image and all of the other information I have been give for the question i have also attached. I have the values for Xmax from a previous question and i have values for K1 at different temperatures. The reactor can be modelled as PFR and so i performed a mole balance over a small element dV to get the volume of the PFR as can be seen in the image. I also calculated molar ratios of all reactants and products and multiplied by P to get partial pressures. I then subbed these in to get the integration as shown. I am using excel and so used trapezium rule to solve the integration however the graphs i get for temperature vs. volume does not seem right and the values for volume seem much too low. Any ideas what i might have done wrong? I've also attached the graph i got for volume against temperature.

First 2 attachments aren't found, and the 3rd could do with being rotated...