1. The problem statement, all variables and given/known data 2. Relevant equations no 3. The attempt at a solution I assumed the path from c to a to be a straight line and I'm unable to find the work as the area in the image above. (sorry my poor english). The book's answer is -2460 J. The answer I found is ≅ -1112 J. My calculations: Va / Ta = Vb / Tb Vb = 3 Va / 2 P = n R Ta / Va ΔUfrom a to c = -800J - P Va / 2 = n (3/2) R (Tc - 200K) Tc = 101.26K Here is the problem. The area in the graph above should be the work done, and it would be equal to (Pa + Pc) (Va - Vb) / 2 I've used Vb because Vc is equal to it. But solving this expression I cant find the answer of the book.