The current price of a stock is $20. In 1 year, the price will be either $26 or $16. The annual risk-free rate is 5%.

The current price of a stock is $20. In 1 year, the price will be either $26 or $16. The annual risk-free rate is 5%. Find the price of a put option on the stock that has a strike price of $21 and that expires in 1 year. (Use daily compounding.)