The average price of gasoline in the U.S. has risen four cents over the past two weeks to $2.25 a gallon for regular grade. Industry analyst said Sunday that retailers and refiners have upped their prices in response to a rise in the cost of crude oil. Still, the average price per gallon is a dime less than it was a year ago. The highest average price for regular is $2.80 in San Francisco. The lowest is $1.91 in Baton Rouge. Nevada averages $2.50 a gallon.