A sample of an ideal gas is taken through the cyclic process $ABCA$ as shown in figure. It absorbs, $40 \mathrm{J}$ of heat during the part $AB$, no heat during $BC$ and rejects $60 \mathrm{J}$ of heat during $CA$. A work of $50 \mathrm{J}$ is done on the gas during the part $BC$. The internal energy of the gas at $A$ is $1560 \mathrm{J}$. The work done by the gas during the part $CA$ is

Read the following statements :
$\mathrm{A}$. When small temperature difference between a liquid and its surrounding is doubled the rate of loss of heat of the liquid becomes twice.

$\mathrm{B}$. Two bodies $P$ and $Q$ having equal surface areas are maintained at temperature $10°\mathrm{C}$ and $20°\mathrm{C}$. The thermal radiation emitted in a given time by $P$ and $Q$ are in the ratio $1:1.15$

$\mathrm{C}$. A carnot Engine working between $100 \mathrm{K}$ and $400 \mathrm{K}$ has an efficiency of $75\%$

$\mathrm{D}$. When small temperature difference between a liquid and its surrounding is quadrupled, the rate of loss of heat of the liquid becomes twice.

Choose the correct answer from the options given below :

In $1^{\mathrm{st}}$${ }^{}$ case, Carnot engine operates between temperatures $300 \mathrm{K}$ and $100 \mathrm{K}$. In $2^{\mathrm{nd}}$${ }^{}$ case, as shown in the figure, a combination of two engines is used. The efficiency of this combination (in $2^{\mathrm{nd}}$${ }^{}$ case) will be :