A stock trades today at $70. After one year, the stock's price will be either $50 or $90. A European derivative will expire after one year. At that time, it will pay $8 if the stock price at that time is $50 and $19 if the stock price at that time is $90. The risk-free rate is 5% per annum compounded annually, but not continuously compounded. What is the price of this derivative?