Oil prices rose on Friday after the U.S. and China seemed to hammer out a trade deal that postponed tariffs. But after studying the details – or lack thereof – investors lost much of their enthusiasm. Crude prices were down at the start of trading on Monday, a reflection of disappointment following last week’s trade announcement. President Trump did his best to sell the deal, arguing that it was the first of a phased approach that would eventually amount to a broad and comprehensive trade agreement. He also encouraged American…