Merger news moved stocks last week. An agreement between US BioEnergy Corp. and VeraSun Energy, the third-largest ethanol producer, sent the stock of US BioEnergy up the most. Bidder VeraSun also got a boost, rising 3 percent Thursday and 7.7 percent Friday. MGI Pharma announced Thursday that it would seek strategic alternatives, and hired Lehman Brothers Holdings Inc. to explore a possible sale. Analyst downgrades on Arctic Cat Inc. put a chill on their stock, making it the biggest loser among mid-caps. Large cap (Market cap greater than $1 billion)LastWeeklyAvg. 5-dayFor the week Companyprice% chg.volume 36weekly gainersBiggest gainer 9weekly losersBiggest loser 0unchangedMost activeMid cap ($100 million to $1 billion) LastWeeklyAvg. 5-dayFor the week Companyprice% chg.volume 16weekly gainersBiggest gainer18weekly losersBiggest loser 0unchangedMost activeSmall cap (less than $100 million) LastWeeklyAvg. 5-dayFor the week Companyprice% chg.volume 11weekly gainersBiggest gainer 10weekly losersBiggest loser 1unchangedMost active$34.6136.9633.09$9.0710.6713.67$13.700.602.11+17.7%-4.0%+5.7%+21.9^-12.5%+5.9%+19.3%-18.9%+3.4%2,712,540627,96013,909,618871,155100,1271,705,61818,96058,625180,346MGI Pharma Inc.Fair Isaac Corp.U.S. BancorpUS BioEnergy Corp.Arctic Cat Inc.American Medical Systems HoldingsIntricon Inc.Innovex Inc.Navarre Corp.