From the graph, the work along the dotted line is irreversible isothermal process in three steps, so work done is sum of pressure– volume work done in each step. Wd = (4 × 1.) + (1 × 1) + (2.5×
2
3
) = 8.65 The work along the solid line is reversible isothermal process, so, Ws = 2 × 2.303 log