Answer these two questions:
how did the mongols promote chinese contact with the rest of the world?

how did the mongols build a vast empire that stretched from europe to china?

The Mongols promoted Chinese contact with the rest of the world by importing Chinese officials and people in power to other areas of the world which were still under Mongol rule. 

They've built this vast empire by employing horse archer tactics which to this day haven't been defeated yet.