Why did the rulers of Moscow work with the Mongols?

i think this is it

Explanation:

When the Mongols invaded the lands of Kievan Rus' in the 13th century, Moscow was an insignificant trading outpost in the principality of Vladimir-Suzdal. Although the Mongols burnt down Moscow in the winter of 1238 and pillaged it in 1293, the outpost's remote, forested location offered some security from Mongol attacks and occupation, while a number of rivers provided access to the Baltic and Black Seas and to the Caucasus region.[10]

The Moscow Kremlin under Prince Ivan Kalita (early XIV century) by Apollinary Vasnetsov

More important to the development of the state of Moscow, however, was its rule by a series of princes who expanded its borders and turned a small principality in the Moscow River Basin into the largest state in Europe of the 16th century.[11] The first ruler of the principality of Moscow, Daniel I (d. 1303), was the youngest son of Alexander Nevsky of Vladimir-Suzdal. He started to expand his principality by seizing Kolomna and securing the bequest of Pereslavl-Zalessky to his family. Daniel's son Yuriy (also known as Georgiy; ruled 1303-1325) controlled the entire basin of the Moskva River and expanded westward by conquering Mozhaisk. He then allied with the overlord of the Rus' principalities, Uzbeg Khan of the Golden Horde, and married the khan's sister.

social status of early civilizations was based primarily on economic power.- true ( first choice)

b.   jim crow laws were enacted in northern states.