Donald Trump's promised 50-foot-tall wall along the U.S.-Mexican border would cost up to US$40 billion, the Massachusetts Institute of Technology (MIT) estimates.

Reuters reports that building 1,000 miles of the wall would require US$9-billion-worth of concrete, according to the MIT study. The steel reinforcements Trump promised would cost an additional $4.6 billion.

Adding labour costs and other expenses, the total cost of the project would come to between $27 billion and $40 billion, MIT estimates.

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