Could you please explain the steps to get to the answer in these problems?

As a gasoline engine is running, an amount of gasoline containing 16,500 J of chemical potential energy is burned in 1 s. During that second, the engine does 3,300 J of work. (a) What is the engine's efficiency (in percent)? % (b) The burning gasoline has a temperature of about 5,000F (3,000 K). The waste heat from the engine flows into air at about 82OF (301 K). What is the Carnot efficiency (in percent) of a heat engine operating between these two temperatures? %