A Carnot engine used first an ideal monoatomic gas ($\mathrm{\gamma } = \frac{5}{3}$) and then an ideal diatomic gas ($\mathrm{\gamma } = \frac{7}{5}$) as its working substance. The source and sink temperatures are ${411}^0\mathrm{C} \mathrm{and} {69}^0\mathrm{C}$ respectively and the engine extracts 1000 J of heat from the source in each cycle. Then

• A

  the efficiency of the engine in the two cases are in the ratio 2l :25

• B

  the area enclosed by the P-V diagram in the first case only is 500 J

• C

   the area enclosed by the P-V diagram in both cases only is 500 J

• D

  the heat energy rejected by the engine in the first case is 600 J while that in the second case is 714.3 J