Engine efficiency, work, power output?

Question

A heat engine absorbs 1704 J from a hot reservoir and expels 1196 J to a cold reservoir in each cycle.
(a) What is the engine's efficiency?
______%
(b) How much work is done in each cycle?
______J
(c) What is the power output of the engine if each cycle lasts for 0.299 s?
_____W

Answer 1

(a) Engine efficiency = ( Useful work done) / Power input =
= (1704-1196) / 1704 = 508 / 1704 = 29.81 %
(b) Useful work done per cycle = (1704-1196) = 508 J
(c) Power output = No. of cycles per sec * Useful work done per cycle
= 508/0.299 = 1699 W

Answer 2

The engine does 1704 - 1196 J of work per cycle. The efficiency is what you get out divided by what you put in:

( 1704 - 1196 ) / 1704

Power is work divided by time.