Suppose Hewlett Packard's stock price is currently $20. In the next six months it will either fall to $10 or rise to $40. What is the current value of a six-month call option with an exercise price of $12? N.B. The six-month risk-free interest rate (periodic rate) is 5%. (Hint: Use the risk-neutral valuation method) $9.78 $11.78 $16.88 $10.28 O $13.33