Mexican billionaire Carlos Slim and former New York City Mayor Michael Bloomberg take part in an event discussing Mexico's relationship to the U.S., in Mexico City, Thursday, Dec. 1, 2016. Bloomberg and the mayors of dozens of the world's largest cities were gathering this week at the C40 Mayors Summit in Mexico City to discuss concrete steps to achieve the carbon emission-reducing goals set by world leaders in Paris. (AP Photo/Marco Ugarte)
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