help in physics

Question

As a gasoline engine is running, an amount of gasoline containing 12,000 J of chemical potential energy is burned in 1 s. During that second, the engine does 4,000 J of work.

(a)

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

 %

(b)

The burning gasoline has a temperature of about 5,000°F (3,000 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) eff = Pout/Pin = 4000/12000 = 1/3 =33%

b) eff =1-Tlow/Thigh= 1-304/3000=.898 =90%