By Pete Najarian, co-founder of OptionMonsterNEW YORK -- Investors are positioning for a rally in Assured Guaranty ( AGO), which trades for barely half its book value. OptionMonster's tracking systems detected the purchase of about 8,000 December 14 calls for 87 cents and the sale of an equal number of December 17 calls for 22 cents. Volume was more than triple open interest at both strikes, which means that new positions were initiated. Those investors now have the right to buy AGO for $14 and have agreed to sell it for $17 if it closes above that level six weeks from now. They paid 65 cents to control this call spread and will collect $3 if it goes to $17--a profit of about 362% from a 30% move in the stock, which shows the kind of leverage you get from trading options. Assured Guaranty's shares fell 2.03% to $13.01 Tuesday. The company provides credit-protection products to financial markets in the United States, Europe, and Australia. Almost 20,000 contracts traded in the name Tuesday, compared with 4,700 in a normal session. Calls outnumbered puts by 6 to 1, reflecting the bullish sentiment. Najarian has no positions in AGO.