Final answer:
The Mongols and Tanguts had a trade dispute over tariffs. The Mongols implemented favorable economic and social policies for merchants and established a postal-station system to assist them during their travels.
Step-by-step explanation:
The Mongols and Tanguts had a trade dispute over tariffs. The Mongols implemented favorable economic and social policies for merchants, who had a higher status under Mongol rule and were not faced with confiscatory taxation like during the rule of traditional Chinese dynasties. Additionally, the Mongols established a postal-station system that provided rest and supplies for merchants during their travels. Under Mongol rule, merchants enjoyed a higher status than during traditional Chinese dynasties due to more favorable tax policies and infrastructure like the postal-station system.