What is the efficiency of a Carnot engine working between the boiling point and the freezing point of water (in $\%$)?

The temperature of the sink of a Carnot engine is $300 \,K$ and the efficiency of the engine is $0.25$. If the temperature of the source of the engine is increased by $100 \,K$, the efficiency of the engine increases by:

$A$ Carnot engine whose efficiency is $40 \%$, receives heat at $500 \ K$. If the efficiency is to be $50 \%$, the source temperature for the same exhaust temperature is (in $K$)

$A$ Carnot engine working between $400 \, K$ and $800 \, K$ has a work output of $1200 \, J$ per cycle. What is the amount of heat energy supplied to the engine from the source per cycle in $J$?

$A$ Carnot engine with efficiency $50\%$ takes heat from a source at $600\text{ K}$. To increase the efficiency by $20\%$, keeping the temperature of the sink the same, the new temperature of the source will be: (in $\text{ K}$)

The efficiency of a Carnot engine which operates between the two temperatures $T_1 = 500 \text{ K}$ (source) and $T_2 = 300 \text{ K}$ (sink) is: (in $\%$)