An engine operates on the cycle shown in the PV diagram below. The working substance of the engine is an ideal monatomic gas. The processes A → B and C → D are isobaric, while processes B → C and D → A are isochoric.
What is the efficiency of a Carnot engine operating between the same maximum and minimum temperatures as this engine?
(A) 1/6
(B) 1/3
(C) 1/2
(D) 3/5
(E) 5/6