) A butterfly spread is the purchase of one call at exercise price X1, the sale of two calls at exercise price X2 and the purchase of one call at exercise price X3. X1 is less than X2 and X2 is less than X3 by equal amounts and all calls have the same expiration date. The price of the underlying asset at maturity is ST. Graph the payoff to this strategy as a function of ST. [Hint: You can form first a payoff table with four different scenarios and then make the plot] [5 marks]