He was going to the quarry to see if they also used copper coins for transactions. If so, he would take his silver and exchange it for copper coins first, then use the copper coins to pay, making a profit on the difference.,Yan Yu squeezed in to join the crowd. She climbed onto a large rock and stood tall, and no one seemed to mind.,He pulled out another thin slate and showed it to everyone: "There are also these kinds. The foreman at the quarry said that these slates can be used for heating floors."。