10 Brian Campbell invested $4,000 and borrowed $4,000 to purchase shares in a large retailing company. At the time of investment, the stock was selling for $45 a share. a. If Brian paid $70 commission, how many shares could he buy if he used only his own money and did not use margin? b. If Brian paid $100 commission, how many shares could he buy if he used his $4,000 and borrowed $4,000 on margin to buy the retailing company's stock? C. Assuming that Brian did use margin, paid $250 commission to buy and sell his stock, and sold his stock for $53, how much profit did he make on his retailing company's investment