N. Call options on a stock are available with strike prices of $15. S171/2, and $20 and expiration dates in three months. Their prices are 54. S2. and $1/2, 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. B/A stock price is currently $50. Over each of the next two three-month periods, it is expected to go up by 6% or down by 5%. The risk-free interest rate is 5% per annum with continuous compounding. What is the value of a six-month European call option with a strike price $51.