New York (CNN Business)Berkshire Hathaway, the massive conglomerate run by billionaire Warren Buffett, posted a nearly $50 billion net loss in the first quarter -- the biggest loss ever for the storied company. Berkshire, which owns companies including Geico auto insurer, Burlington Northern Santa Fe railroad, Dairy Queen, Duracell and many other financial, industrial and consumer firms, has been hit hard by the Covid-19 pandemic. Just like the rest of the market and economy. The company said in a regulatory filing Saturday morning that before the coronavirus hit the United States in mid-March, many of Berkshire's businesses were posting revenue...