It never fails to amaze how little U.S. President Donald Trump, that lifelong businessman, understands about business. The most recent example took place in the Oval Office late Monday morning after his televised phone call with Mexican President Enrique Pena Nieto. The two men were congratulating each other for reaching an agreement on a trade deal that is meant to eventually replace the North American Free Trade Agreement.

Canada, of course, is also part of NAFTA, but while Pena Nieto stressed the importance of getting Canada on board, Trump seemed indifferent. "We'll see if Canada can be part of the deal," he said. If it negotiates "fairly," Trump added, his team would open negotiations immediately, hoping to complete a deal by Friday. (Friday?) And if not? Well, then, the U.S. and Mexico would have a bilateral deal, and Canada would be punished.

"I think the easiest thing is to tariff their cars," said the president of the United States.