Amid plunging oil prices in the fourth quarter of 2014, Warren Buffett's Berkshire Hathaway exited its positions in both Exxon Mobil and ConocoPhillips. Berkshire sold 41 million shares of Exxon worth more than $3.7 billion, according to a new regulatory filing with the Securities and Exchange Commission. Its position in Exxon was the eighth-largest in its portfolio prior to being liquidated. Berkshire's holding in ConocoPhillips was a smaller 472,000 shares. It reduced its holding in oil and gas drilling equipment manufacturer National Oilwell Varco as well. The company's profits or losses on the positions were not disclosed. Oil prices fell about 48% last year.