From the following $P-T$ graph,what inference can be drawn?

$2 \, g$ of ${O_2}$ gas is taken at $27^{\circ}C$ and a pressure of $76 \, cm$ of $Hg$. Find the volume of the gas (in liters).

When the pressure of the gas contained in a closed vessel is increased by $2.5 \%$,the temperature of the gas increases by $4 \ K$. The initial temperature of the gas is (in $K$)

The expansion of an ideal gas of mass $m$ at a constant pressure $P$ is given by the straight line $B$ in the $V-T$ graph. Then the expansion of the same ideal gas of mass $2m$ at a pressure $2P$ is given by the straight line:

For one gram mole of a gas,the value of $R$ in the equation $PV = RT$ is nearly ...... $cal/K$

In the given $(V - T)$ diagram,what is the relation between pressures $P_1$ and $P_2 \,?$