With what the internal energy of real gases be determined ?

For one complete cycle of a thermodynamic process on a gas as shown in the $P-V$ diagram, Which of following is correct

A thermodynamic system is taken from an original state to an intermediate state by the linear process shown in Figure.

Its volume is then reduced to the original value from $E$ to $F$ by an isobaric process. Calculate the total work done (in $J$) by the gas from $D$ to $E$ to $F$

$n$ mole a perfect gas undergoes a cyclic process $ABCA$ (see figure) consisting of the following processes.

$A \rightarrow B :$ Isothermal expansion at temperature $T$ so that the volume is doubled from $V _{1}$ to $V _{2}=2 V _{1}$ and pressure changes from $P _{1}$ to $P _{2}$

$B \rightarrow C :$ Isobaric compression at pressure $P _{2}$ to initial volume $V _{1}$

$C \rightarrow A$ : Isochoric change leading to change of pressure from $P _{2}$ to $P _{1}$

Total workdone in the complete cycle $ABCA$ is

Work done in the given $P-V$ diagram in the cyclic process is