Trump touts tariffs as trade leverage. But what do U.S. farmers and retailers think?

Summary: President Trump has spent much of his term confronting other countries over trade practices. In particular, he is engaged in a bitter tariff war with China. But how do these tensions affect the U.S. economy? William Brangham talks to Iowa farmer Denny Friest and the National Retail Federation's David French about what they see in agriculture and retail -- two sectors caught in the crossfire.