Check out the companies making the biggest moves premarket: Occidental Petroleum , Berkshire Hathaway — Occidental gained around 1% after Berkshire Hathaway announced it was buying the oil company's petrochemical division, OxyChem, for nearly $10 billion in cash . Class B shares of Berkshire Hathaway slipped about 0.2%. Fair Isaac — The stock rallied 19% after the company unveiled a system that allows mortgage lenders direct access to FICO scores. Credit bureaus Transunion and Equifax shed 11% each. Curbline Properties — The real estate trust rose more than 2% after it authorized a share repurchase program of up to $250 million. Celanese — The materials company rose more than 2% after Citi upgraded the stock to buy from neutral. "Despite the sluggish macro backdrop, we see continued self-h

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