Which of the following graphs between pressure $(P)$ and volume $(V)$ correctly shows isochoric changes?

The $P-V$ diagram for an ideal gas in a piston-cylinder assembly undergoing a thermodynamic process is shown in the figure. The process is

$A$ sample of an ideal gas $(\gamma = 5/3)$ is heated at constant pressure. If $100 \ J$ of heat is supplied to the gas,the work done by the gas is: (in $J$)

$A$ diatomic gas $\left(C_P = \frac{7}{2} R\right)$ does $200 \ J$ of work when it is expanded isobarically. The heat given to the gas in the process is (in $J$)

Calculate the work done when the volume of a gas increases by $0.25\,m^3$ at a constant pressure of $10^3\,N/m^2$.

$n$ moles of an ideal gas with constant volume heat capacity $C_v$ undergo an isobaric expansion by a certain volume. The ratio of the work done in the process to the heat supplied is