By David Russell, reporter at OptionMonsterNEW YORK -- Bullish traders piled into International Paper ( IP) again Monday. OptionMonster's tracking systems detected the purchase of about 15,000 January 38 calls, most of which priced for $1.58. Roughly the same number of January 42 calls were sold at the same time for 46 cents. Volume was more than 10 times open interest at both strikes, indicating that new positions were initiated. Owning calls locks in the price where an investor has a right to buy a stock, while selling them obligates him or her to sell shares if they go above a certain level. In the case of Monday's bullish call spread, the trader has the right to buy International Paper for $38 but must the stock for $42 if it goes that high by mid-January. This spread cost $1.12 to open, which would translate into a profit of 257% if the paper company closes at or above $42 at expiration. That's less than 20% above Monday's $36.16 closing price, which shows the kind of leverage that can be generated with options. Investors have already been making money in the name after paying just 80 cents for the October 35 calls in mid-September. Those premiums more than tripled to $2.39 by later in the month. Overall option volume was quadruple the daily average, with this trade accounting for most of the activity. Calls outnumbered puts by a bullish 9-to-1 ratio, according to our data systems. Russell has no positions in IP.