Oil prices slipped in early trade on Friday but were on track for gains of more than six per cent for the week on solid signs of demand growth in top crude-oil importer China and expectations of less aggressive interest rate rises in the United States. Brent crude futures had fallen 33 cents, or 0.4pc, to $83.70 a barrel by 0322 GMT, while US West Texas Intermediate (WTI) crude futures slipped