Using Margin. Bill Campbell invested $4,000 and borrowed $4,000 to purchase shares in Kellogg. At the time of his investment, Kellogg stock was selling for $50 a share.

a. If Bill paid a $50 commission, how many shares could he buy if he used his $4,000 and borrowed $4,000 on margin to buy Kellogg stock?

b. Assuming Bill did use margin, paid a $90 total commission to buy and sell his Kellogg stock, and sold his stock for $65 a share, how much profit did he make on his Kellogg investment?