What is the engine's efficiency (in percent)?

Question

As a gasoline engine is running, an amount of gasoline containing 10,200 J of chemical potential energy is burned in 1 s. During that second, the engine does 3,400 J of work.

(a)What is the engine's efficiency (in percent)?

(b)The burning gasoline has a temperature of about 4,200°F (2,600 K). The waste heat from the engine flows into air at about 88°F (304 K). What is the Carnot efficiency (in percent) of a heat engine operating between these two temperatures?

Answer 1

(a) k = (10200J - 3400J)/10200J·100% = 66.67%

(b) k = (2600K - 304K)/2600K·100% = 80.31%