Berkshire Hathaway Inc. (BRK/A) reported a stake in Exxon Mobil Corp. (XOM) valued at about $3.7 billion as Warren Buffett ’s company disclosed its largest new holding since adding International Business Machines Corp. in 2011. Buffett’s company owned 40.1 million shares of Exxon on Sept. 30, Omaha, Nebraska-based Berkshire said today in a regulatory filing. The world’s biggest oil company by market value closed at $93.22 today in New York . It rose to $93.90 in extended trading at 5:14 p.m., after the filing. Berkshire has benefited this year as its stock picks rallied along with the broader market, affirming a strategy of favoring equities instead of bonds amid near record-low interest rates. Buffett has tracked Exxon and bought its stock in the past, holding a stake in the Irving, Texas-based energy producer as recently as 2011. Exxon Mobil “is undervalued, in his opinion, and pretty much being ignored […]