Ruby function for Option value calculation

class Stock
	def initialize (initial_price = 100, up = 1.04574)
		@initial_price = initial_price
		@up = up
		@down = 1/up
	end
	def calculateStock (n)
		Array.new(n + 1) {|i| @initial_price * (@up**( n - i))*(@down**i)}
	end
	def calculateOption (n, t = 0, strike = 100, r = 1.0005, call = -1)
		q = (r - @down) / (@up - @down)
		q1 = 1- q
		stock_price_n = calculateStock (n)
		option_price_n = stock_price_n.map { |i| [(i - strike)*call, 0].max }
		array_length = n + 1
		(t..(n-1)).each{ |index|
			array_length = array_length - 1
			option_price = calculateStock (array_length - 1).map { |i| [(i - strike)*call, 0].max }
			option_price_n = Array.new(array_length) {|i| 
			    [(option_price_n[i] * q + option_price_n[i+1] * q1)/r, option_price[i]].max 
			}			
		}
		option_price_n
	end	
end

stock = Stock.new
#print stock.calculateStock (0)
#print stock.calculateStock (1)
#print stock.calculateStock (2)
print stock.calculateOption (10)
#print stock.calculateOption (5)
#print stock.calculateOption (6)