After months of dropping, gas prices are back on the upswing. The average price of a gallon of gasoline in the U.S. has risen seven cents in the last three weeks. That's according to the Lundberg Survey  which puts the price of a gallon of regular at $3.32. Of the places surveyed in the lower 48 states, Salt Lake City has the nation's lowest average price at $3.04. Long Island New York  has the highest at $3.75.