A knockout call option loses all value at the instant the price of the stock drops below a given “knockout level.” Determine a fair price for a knockout call option when the current stock price is $20, the exercise price is $21, the knockout price is $19.50, the mean annual growth rate of the stock is 12%, the annual volatility is 40%, the risk-free rate is 10%, and the exercise date is one month from now (where you can assume there are 21 trading days in the month and 250 in a year).