Occidental Petroleum shares were steady in premarket trade after Berkshire Hathaway disclosed it bought another 9.5 million shares, to take its stake to 152.7 million shares. Berkshire Hathaway’s stake in Occidental is valued at $8.5 billion. Occidental shares have surged 92% this year, though the stock is off 23% from its May 31 peak as oil prices have receded.

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