Bob Orleans invested $$10,000$ and borrowed $$10,000$ to purchase shares in Verizon Communications. At the time of his investment, Verizon was selling for $$50$ a share.

a$.$ If Bob paid a commission of $$50,$ how many shares could he buy if he used only his own money and did not use margin?

Number of shares

b$.$ If Bob paid a commission of $$100,$ how many shares could he buy if he used his $$10,000$ and borrowed $$10,000$ on margin to buy Verizon stock?

Number of shares

c$.$ Assume Bob did use margin to buy his Verizon stock. Also, assume he paid another $$100$ to sell his stock and sold the stock for $$57$ a share. How much profit did he make on his Verizon stock investment?

Profit