I want to know the answer to the following question:
What king ruled Persia in 520 BC?
All the background I'm provided with is that "By 520 BC, during the reign of Darius I of Persia, much of the northwestern subcontinent (present-day eastern Afghanistan and Pakistan) came under the rule of the Persian Achaemenid Empire, as part of the far easternmost territories.". Is that enough to answer the question?