Bob Orleans invested $$3,000$ and borrowed $$3,000$ to purchase shares in Verizon Communications. At the time of his investment, Verizon was selling for $$60$ a share.

a$.$ If Bob paid a commission of $$20,$ how many shares could he buy if he used only his own money and did not use margin? $($Round your answer to nearest whole number.$)$

b$.$ If Bob paid a commission of $$40,$ how many shares could he buy if he used his $$3,000$ and borrowed $$3,000$ on margin to buy Verizon stock? $($Round your answer to nearest whole number.$)$

c$.$ Assume Bob did use margin to buy his Verizon stock. Also, assume he paid another $$40$ to sell his stock and sold the stock for $$64$ a share. How much profit did he make on his Verizon stock investment? $($Round intermediate calculations to nearest whole number. Round your answer to nearest whole dollar.$)$