What is the molar volume of a gas? What is its value taken as?

Identify the correct observation with respect to the given graphs.

The minimum pressure required to compress $600 \; dm^{3}$ of a gas at $1 \; bar$ to $150 \; dm^{3}$ at $40^{\circ} C$ is ......... $bar$.

Which of the following expressions at constant pressure represents Charles's law?

Pay load is defined as the difference between the mass of displaced air and the mass of the balloon. Calculate the pay load when a balloon of radius $10 \, m$,mass $100 \, kg$ is filled with helium at $1.66 \, bar$ at $27^{\circ} C$. (Density of air $= 1.2 \, kg \, m^{-3}$ and $R = 0.083 \, bar \, dm^{3} \, K^{-1} \, mol^{-1}$).

Match the following graphs of an ideal gas with their respective axes ($X$ and $Y$).
$(A)$ $P$ vs $V$ (at constant $T$)
$(B)$ $V$ vs $T$ (at constant $P$)
$(C)$ $P$ vs $T$ (at constant $V$)
List-$I$:
$(1)$ $P$ on $Y$-axis,$T$ on $X$-axis
$(2)$ $P$ on $Y$-axis,$1/V$ on $X$-axis
$(3)$ $V$ on $Y$-axis,$T$ on $X$-axis