What is the thermal efficiency of the heat engine illustrate

What is the thermal efficiency of the heat engine illustrated on the pV diagram below? The gas is monatomic. 2/13 8/9 2/9 1/3 8/13

Solution

Net Work done W = Area of rectangle

                           = (4Pa-2Pa)(4-2)m ³

                           = 2Pa x 2 m ³

                          = 4 J

Heat added Q = Area under top line and volume axis

                     = 4 Pa x(4-2)m ³

                     = 4 Pa x 2 m ³

                    = 8 J

Thermal efficiency = W/Q

                           = 4 J / 8 J

                           = 1/2