Hi Class,
I realized I made a slight mistake on Wednesday in my solution for #1. That mistake gave me a total positive work (while it should be negative for such a cycle). The root of the mistake was that I took V1 to be the experimentally observed critical volume rather than the theoretical (van der Waals) critical volume. Thus, the equation of state was violated at the critical point, and an erroneous process was obtained. I made the corresponding corrections in the solution (it should be posted later today).
-Avi