Consider two identical plastic foam balls each one having a thin sheath of aluminium foil. One of the balls has a few positive charges and the other has the same amount of negative charge. Each of the charge resides on the aluminium foil. Each one ball is on the end of its own thin glass rod which serves as a handle. A person carries one of the balls in contact with the other and then separates them. What is the symbol of the charge on the ball that was originally charged positively?