GENESEE COUNTY — Average retail gasoline prices in Michigan have risen 8.3 cents per gallon in the past week, averaging $3.83 a gallon. This compares with the national average that has risen 5.9 cents per gallon in the last week to $3.67 a gallion, according to gasoline price website www.MichiganGasPrices.com. Including the change in gas prices in Michigan during the past week, prices yesterday were $1.07 per gallon higher than the same day one year ago and are 6.2 cents per gallon lower than a month ago. The national average has decreased 0.7 cents per gallon during the last month and stands 98.2 cents per gallon higher than this day one year ago. — G.G.