Since last summer, Bob Dudley, the CEO of the British oil giant BP, has been cautioning that he expects oil prices to stay “lower for longer.†Now he believes he’s determined how much longer those prices may decline, and when they may start rising again. “A low point could be in the first quarter [of 2016],†Dudley said in an interview broadcast Saturday by the BBC. “But 2016’s third and fourth quarters could witness a more natural balance between supply and demand, after which stock levels could start to wear off.â€