LONDON - World oil prices slid Thursday as investors nervously awaited this week's crucial speech from Federal Reserve chairman Ben Bernanke. Brent North Sea crude for delivery in October dropped 26 cents to $112.28 a barrel in late afternoon London deals. New York's main contract, West Texas Intermediate (WTI) light sweet crude for October, retreated $1.53 to $93.96 a barrel. Attention is now on a meeting of central bankers at Jackson Hole, Wyoming, where Bernanke is due to give a speech on Friday, with investors hoping he will outline plans for another round of monetary easing to kickstart the US economy.