Answer
See answers.
Work Step by Step
The first step, from 1 to 2, is an isothermal expansion. The volume increases, the pressure decreases, and the temperature stays the same.
The second step, from 2 to 3, is at constant volume because no work is done. On a PV graph, it is a vertical line.
The third and final step, from 3 back to 1, is adiabatic (Q is 0) and is a compression, since the work W is negative.