How did the inca develop their road system

The Inca road system was a vital part of the Inca empire. In fact, it actually contributed significantly to shape that empire. It consisted of a very extensive network of roads, both main and secondary, that, emanating from the city of Cuzco, the empire capital, covered a geographically diverse and extensive area (24,000 miles) with the goal of transporting people (armies, administrative personnel, captives), goods and information throughout every part of the kingdom. Ancient roads, some of them over a thousand years old, were used, improved and expanded to create this extensive network. Due to the geography of the terrain, bridges of different kinds had to be built, using trunks, fibers and other natural materials. In addition, only materials such as stone, wood, earth, sand and even grass, and rudimentary tools together with the hands of hundreds of workers, made possible this astonishing, and surprisingly lasting, feat of engineering. Still today it is possible to see and use very large sections of the network.    

the answer is 1.. i think

i think that it would be tenth of the first