The basket price of the Organization of the Petroleum Exporting Countries (OPEC) on Friday retreated slightly from its eight-months high but stayed above $70 last Friday, the Vienna-based group announced Monday. One barrel (159 liters) of OPEC-produced crude oil stood at $70.45 Friday, down from $70.87 on the previous day, when the price had reached its highest level since mid-October of last year. The cartel produced 33.9 per cent of the world's oil supply in May, according to OPEC's latest market report quoted by the German news agency "DPA."