The shown $p-V$ diagram represents the thermodynamic cycle of an engine, operating with an ideal mono atomic gas. The amount of heat, extracted from the source in a single cycle is

One mole of diatomic ideal gas undergoes a cyclic process $ABC$ as shown in the figure. The process $BC$ is adiabatic. The temperatures at $A, B$ and $C$ are $400 \mathrm{K}, 800 \mathrm{K}$ and $600 \mathrm{K}$, respectively. Choose the correct statement.

A solid body of constant heat capacity $1 \mathrm{J} {}^{\circ }\mathrm{C}^{-1}$ is being heated by keeping it in contact with reservoirs in two ways
(i) Sequentially keeping in contact with $2$ reservoirs such that each reservoir supplies the same amount of heat.
(ii) Sequentially keeping in contact with $8$ reservoirs such that each reservoir supplies the same amount of heat.

In both the cases, the body is brought from initial temperature $100 °\mathrm{C}$ to final temperature $200 °\mathrm{C}$. Entropy change of the body in the two cases respectively, is

$5.6 \mathrm{litre}$ of helium gas at S.T.P. is adiabatically compressed to $0.7 \mathrm{litre}$. Taking the initial temperature to be $T_1,$ the work done in the process is,

Two moles of ideal helium gas are in a rubber balloon at $30°\mathrm{C}.$ The balloon is fully expandable and can be assumed to require no energy in its expansion. The temperature of the gas in the balloon is slowly changed to $35°\mathrm{C}.$ The amount of heat required in raising the temperature is nearly $(\mathrm{take} R=8.31\mathrm{J}/\mathrm{molK}):$