$(7$ points$)$ Call options on a stock are available with strike prices of $$5,$$$10,$ and $$15$ and

expiration dates in three months. Their prices are $$6,$$$1\mathrm{.}5,$ and, $$1$ respectively.

Explain how the options can be used to create a butterfly spread.

Construct a table showing how profit varies with stock price for the butterfly spread.