Warren Buffett has given away $3.4 billion in Berkshire Hathaway Inc. BRK.A, -0.34% BRK.B, +0.54% stock, the company said late Monday. Buffett converted roughly 10,000 class A shares into 17.8 million class B shares and donated them to five foundations, including the Bill & Melinda Gates Foundation. Buffett made a pledge to donate shares to various foundations in 2006 and has given away $31 billion in stock, according to Berkshire Hathaway. Berkshire Hathaway class B stock is down 1% after hours and closed up 0.5% to $192 during regular trading. The benchmark S&P 500 index SPX, -0.10% closed down 0.1%.