The price of oil sank toward $89 a barrel Monday as a flare-up in Europe's debt crisis and concern over Chinese economic growth suggested demand for crude will weaken. The benchmark crude futures contract for September delivery was down $2.55 at $89.28 a barrel by late morning European time in electronic trading on the New York Mercantile Exchange. The August contract, which expired Friday, ended down $1.22 at $91.44 per barrel in New York. Brent crude was down $2.76 at $104.07 a barrel on the ICE futures exchange in London, according to a report of the Associated Press. In other energy trading, gasoline was down 6.8 cents at $2.88 a gallon and heating oil fell 7.1 cents to $2.85 a gallon. Natural gas was down 3.1 cents at $3.05 per 1,000 cubic feet.