Is an adiabatic process
TVγ−1=const⇒VTγ−11=const
⇒ as T increase V decreases at non-uniform rate
In process a→b P = constant as V∝T
In process c→d P′= constant s V∝T
But since slope of V - T graph ∝P1
since slope of ab < slope of cd
⇒Pab>Pcd
Also in adiabatic process d→a as T is increasing V in decreasing
⇒ P is increasing, so P - V diagram is as below





