A Heat Engine Takes 2

A heat engine takes 2.0 moles of an ideal gas through the reversible cycle abca,on the pV diagram shown in the figure.The path bc is an isothermal process.The temperature at c is 820 K,and the volumes at a and c are 0.010 m³ and 0.16 m³,respectively.The molar heat capacity at constant volume,of the gas,is 37 J/mol ∙ K,and the ideal gas constant is R = 8.314 J/(mol ∙ K) .The thermal efficiency of the engine is closest to

A) 0.26.
B) 0.026.
C) 0.33.
D) 0.40.
E) 0.53.