Herbert Corporation is a non-dividend-paying stock that is currently priced at $82. An analyst has determined that the annual standard deviation of returns on Herbert stock is 31% and that the annual risk-free interest rate on a continuously compounded basis is 3.5%. What is the percentage down movement using a two-step binomial model to value an 18-month option?

	A.	17%
	B.	21%
	C.	32%
	D.	24%