Crude oil prices slipped to under $99 per barrel Monday, as equities floundered around the globe due to a prolonged lack of a solution to debt issues in Europe. On the New York Mercantile Exchange, West Texas Intermediate crude shed 84 cents to reach $98.72 per barrel. Home heating oil added 0.24 cents $3.0617 per gallon. Reformulated blendstock gasoline lost 3.21 cents to $2.8913 per gallon. Henry Hub natural gas prices gained 1.8 cents to $2.774 per million British thermal units. At the pump, the national average price of unleaded gasoline added one penny overnight, jumping from $3.419 per gallon to $3.429, AAA said.