40 under 40

Our 2013 edition of the list features young hotshots who are rocking businesses as diverse as air travel, natural gas, and genetic coding, as well as—if you can believe it— government.

9. Tracy Britt Cool

40u40 main tracy britt
  • Age: 29
  • Title: Financial Assistant to the Chairman
  • Company: Berkshire Hathaway

Ever since Warren Buffett hired Cool, the daughter of Kansas farmers, out of Harvard Business School in 2009, he has heaped responsibilities on her. He named her chairman of four Berkshire-owned companies— Benjamin Moore, Johns Manville, picture-framer Larson-Juhl, and Oriental Trading—and recently put her on the board of H.J. Heinz. "She's a blotter for learning," says Buffett.

  @FortuneMagazine - Last updated September 30 2013 03:41 PM ET
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