Joe Biden's first and last trip to Africa as president wrapped up in a port city in Angola. It's the end of an 800 mile train line connecting the port to massive mineral deposits in Central Africa. The U.S. and other Western countries are raising billions to upgrade the rail line, a move that is seen as an effort to counter China's investments in mining in the region. We go to one of the mining cities along that train route to see how the geopolitics are playing out.

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