Through Liberty bonds.
Hope this helps! :D
Sorry I'm late, but for other people with this question the answer is A: City Y is in the middle of a continent and City X is on the coast.
The primary purpose was always to protect the Chinese Empire from the Mongolians and other invaders. Most of the current Great Wall we see today was built in the Ming Dynasty (1368-1644) and is approximately 6000km long.
Germany...................
