4) (15 pts) The price of a stock is S(0) = $40. You are to price a call and put option, using a one-step binomial model. The stock is assumed to either increase to $50 or decrease to $25. Both options expire in three months, have a strike price equal to the price of the stock, and the risk-free rate is r = 5%. Illustrate the model, deve risk-neutral probabilities, evaluate the price of the call and put, and verify that pure parity is met