By David Russell, reporter at OptionMonsterNEW YORK -- Viacom ( VIAB) has been going straight up along with other media names, and the bulls expect more gains in the next month. OptionMonster's tracking programs detected the purchase of about 12,000 May 70 calls Monday, with the largest block priced for 70 cents. This is clearly fresh buying, as the volume dwarfed the strike's open interest of just 337 contracts before the session began. Calls provide inexpensive upside exposure because they lock in the price where shares can be bought. They can generate significant leverage if the stock climbs but will expire worthless if it doesn't in the next month. Viacom shares fell 3.73% to $64.02 Monday but are up 21% so far this year. The company, whose brands include MTV, Comedy Central and VH1, reports earnings on May 1. Total option volume was nine times greater than average in the stock on Monday, with calls outnumbering puts by a bullish 27 to 1. Russell has no positions in VIAB.