The current stock price of Alcoa is $20, and the stock does not pay dividends. The instantaneous risk-free rate of return is 3%. The instantaneous standard deviation of Alcoco's stock is 45%. You want to purchase a put option on this stock with an exercise price of $25 and an expiration date 30 days from now. According to the Black-Scholes OPM, you should hold __________ shares of stock per 100 put options to hedge your risk.