Oil prices sank again on Monday, giving consumers more of a break and causing a split among OPEC leaders about what action should be taken, if any, to halt the slide. The price drop has led to a near free fall in gasoline prices in the United States. On Monday, the national average price for regular gasoline was $3.20, 9 cents lower than it was a week ago and 14 cents below the price a year ago, according to the AAA motor club.