Reversible work:
For constant pressure:
I
For constant T step:
II
Therefore, for overall path:
I+II
Consider a Carnot Cycle:
Step: A® B
Add heat (T1)
B® C
Expand to T2
(adiabatically) 
C® D
Remove heat (T2)
D® A
Compress to T1
(adiabatically)