Call options on a stock are available with strike prices of $$15,$ $$17\mathrm{.}5$ and $$20$ before expiration date. The call premiums for each are $$4,$ $$2$ and $$0\mathrm{.}5$ respectively. Explain how the options can be used to create a butterfly spread. A$.$ Construct a table showing how profit varies with stock price for the butterfly spread. B$.$Plot the profit with stock price for the butterfly spread. List the profit formula for each trend.