A friend of yours learns that you are taking BUS$-123,$ Introduction to Investments. He tells you that he has been trading using Robinhood. He makes several trades each week. He says that there are no commissions so he can make as many free trades as he wants since there are no transaction costs. He asks for your opinion. What can you tell him about Robinhood and commission$-$free trades? Is he really not paying anything to trade stocks?