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David Koch, executive vice president of chemical technology for Koch Industries Inc., center and wife Julia Flesher, left, speak with a guest during the Memorial Sloan-Kettering Cancer Center 5th Annual Spring Ball at the Metropolitan Museum in New York, U.S., on Wednesday, April 25, 2012. The Spring Ball celebrates the hard work and dedication of the Cancer Center. Photographer: Amanda Gordon/Bloomberg via Getty Images

David Koch, executive vice president of chemical technology for Koch Industries Inc., center and wife Julia Flesher, left, speak with a guest during the Memorial Sloan-Kettering Cancer Center 5th Annual Spring Ball at the Metropolitan Museum in New York, U.S., on Wednesday, April 25, 2012. The Spring Ball celebrates the hard work and dedication of the Cancer Center. Photographer: Amanda Gordon/Bloomberg via Getty Images