TOPEKA, Kan. (WIBW) – Gas prices are down slightly this week across the nation, including in the Sunflower State. According to AAA, the average price for a gallon of unleaded gasoline on Tuesday morn ing was $3.16. That’s down 4 cents from $3.20 a week ago and $3.20 a month ago. It’s also down 39 cents from $3,55 a year ago.