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

An ideal gas undergoes the cyclic process $abca$ as shown in the given $P-V$ diagram. It rejects $50 \,J$ of heat during $ab$ and absorbs $80 \,J$ of heat during $ca$. During $bc$, there is no transfer of heat and $40 \,J$ of work is done by the gas. What should be the area of the closed curve $abca$ (in $\,J$)?

$A$ thermodynamic system is taken through the cycle $PQRSP$ process as shown in the figure. The net work done by the system is .... $J$. (Note: $1 \text{ kp} = 10^3 \text{ Pa}$,$1 \text{ cc} = 10^{-6} \text{ m}^3$)

$A$ system goes from $A$ to $B$ via two processes $I$ and $II$ as shown in the figure. If $\Delta U_1$ and $\Delta U_2$ are the changes in internal energies in the processes $I$ and $II$ respectively,then:

What is the net work done in the process shown in the $P-V$ diagram?

$A$ gas system is taken through the thermodynamic cyclic process $1 \rightarrow 2 \rightarrow 3 \rightarrow 1$ as shown in the figure. The amount of heat released by the system is