Crude oil prices lost ground Monday on the New York Mercantile Exchange, dropping 50 cents to $90.90 a barrel in early trading. The price for crude oil settled at $91.40 a barrel Friday, Natural gas picked up a penny to $2.89 per million British thermal units in early trading. Gasoline was off 4 cents from Friday\'s close, trading at $2.89 a gallon during the morning session. Home heating oil also was off, trading 2 cents lower than its Friday settling price of $2.93 a gallon. At the pump, the average cost for a gallon of regular unleaded gasoline jumped to $3.619 per gallon from $3.567 on Friday, AAA reported.