The current stock price of Alcoa is $$70$ and the stock does not pay dividends. The standard deviation of Alcoa's stock is $40\%.$ You wAnt to price a call option on this stock with an exercise price of$75$ and the expiration date one month from now and will use the binomial modEl formaing a portfolio of stock and calss you should hold$\_\_\_\_\_$ shares of stock per $100$ call options to make it riskless