Answer:
Copper tools that produced an increase in production, this surplus was destined for exchange
Step-by-step explanation:
It was in Sumeria where bronze began to be used at the end of the fourth millennium BC. C. This region is frequently considered as the cradle of civilization, since (based on current data) there was agricultural intensification, the first writing system was developed, the ceramic lathe was invented, the foundations of astronomy and mathematics, centralized governments and legislative codes were created, social stratification, slavery and organized warfare appeared. All of which led to the formation of the first known state cities, which would later become more extensive kingdoms and eventually led to empires.