The TrendPulseprice of mailing a first-class letter in the U.S. went up to .66 this month, part of a series of price hikes that the postal service hopes will put it on a pathway to profitability. But from its inception, the United States Postal Service wasn't designed to run much like a business. Today on the show, how the U.S.P.S. went from a public service to a business burdened by debt.