Who first proposed (invented) the Carnot engine?

$A$ Carnot engine has an efficiency of $1/6$. When the temperature of the sink is reduced by $62\,^{\circ}C$,its efficiency is doubled. The temperatures of the source and the sink are,respectively:

$A$ Carnot engine operates between two reservoirs of temperatures $900 \; K$ and $300 \; K$. The engine performs $1200 \; J$ of work per cycle. The heat energy (in $J$) delivered by the engine to the low-temperature reservoir in a cycle is:

$A$ number of Carnot engines are operated at identical cold reservoir temperatures $(T_{L})$. However,their hot reservoir temperatures are kept different. $A$ graph of the efficiency of the engines versus hot reservoir temperature $(T_{H})$ is plotted. The correct graphical representation is

The efficiency of a Carnot engine is $50\%$ and the temperature of the sink is $500\,K$. If the temperature of the source is kept constant and its efficiency is to be raised to $60\%$,then the required temperature of the sink will be ........... $K$.

$A$ Carnot engine working between $300\, K$ and $600\, K$ has a work output of $800\, J$ per cycle. How much heat energy is supplied to the engine from the source in each cycle? .... $J$