The Current Price Of A Non Dividend Paying Stock Is 50 Volatility 20 And The Con

The current price of a non-dividend paying stock is $50, volatility 20% and the continually compounding risk-free rate 5%. Use a two-step tree with 6-month steps to value a) A European put option on the stock with a strike price of $48 that expires in 12 months b) An American put option with the same strike and expiration.