The first law of thermodynamics confirms the law of . . . . . . .

The $P-V$ diagram of a system undergoing a thermodynamic transformation is shown in the figure. The work done on the system in going from $A \to B \to C$ is $50 \, J$ and $20 \, cal$ of heat is given to the system. The change in internal energy between $A$ and $C$ is ...... $J$.

$A$ gas absorbs $18 \ J$ of heat and work done on the gas is $12 \ J$. Then the change in internal energy of the gas is: (in $J$)

When $1500 \ J$ of heat is supplied to a gas at a constant pressure of $2.5 \times 10^{5} \ N/m^{2}$,the volume increases by $2.5 \times 10^{-3} \ m^{3}$. The increase in the internal energy of the gas is ..... $J$?

The change in the internal energy of a mass of gas,when the volume changes from $V$ to $2V$ at constant pressure $P$,is (where $\gamma$ is the ratio of specific heat of gas at constant pressure to specific heat at constant volume):

Assertion : Heat and work are modes of energy transfer to a system resulting in change in its internal energy.
Reason : Heat and work in thermodynamics are state variables.
The correct option among the following is