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NEW YORK, NY - JANUARY 27: Bill Gates and Warren Buffett speak with journalist Charlie Rose at an event organized by Columbia Business School on January 27, 2017 in New York City. Gates and Buffett spoke on a range of topics including their friendship, business, philanthropy, global health, innovation, and leadership. (Photo by Spencer Platt/Getty Images)

NEW YORK, NY - JANUARY 27: Bill Gates and Warren Buffett speak with journalist Charlie Rose at an event organized by Columbia Business School on January 27, 2017 in New York City. Gates and Buffett spoke on a range of topics including their friendship, business, philanthropy, global health, innovation, and leadership. (Photo by Spencer Platt/Getty Images)