Four hypothetical thermal devices are described:
I. A heat engine absorbs heat at 500 K, exhausts heat at 300 K, and produces work with 25% efficiency.
II. A refrigerator removes heat from its 275 K interior and exhausts a greater amount of heat to 300 K room air while using electrical work.
III. A device draws heat from 300 K seawater and converts all of that heat directly into electrical work, with no heat exhaust.
IV. A heat pump moves heat from outdoor air at 280 K into a house at 295 K but requires no electrical work.
Which of the devices, if any, violates the second law of thermodynamics?
a) III only
b) I and III only
c) III and IV only
d) II and IV only