A Carnot engine used first an ideal monoatomic gas then an ideal diatomic gas as working substance. If the source and sink temperature are ${411}^{\mathrm{o}}\mathrm{C} \mathrm{and} {69}^{\mathrm{o}}\mathrm{C}$ respectively and the engine extracts I000 J of heat in each cycle, then area enclosed by the PV diagram is

• A

  100 J

• B

  300 J

• C

  500 J

• D

  700 J