Massachusetts gas prices drop again By Ira Kantor/ BostonHerald.com Monday, December 10, 2012            Bay State gas prices dropped another seven cents this week, according to AAA Southern New England.            Self-serve, regular unleaded gas is currently averaging $3.47 a gallon in Massachusetts, 13 cents above the national average of $3.34.            Local prices are down 14 cents over the past month. A year ago at this time, the Massachusetts average price was $3.27.            Both midgrade unleaded and premium unleaded gas fell six cents this week to $3.68 and $3.80 a gallon, respectively. Diesel remained unchanged at $4.08 a gallon.            The range in prices in the latest AAA survey for unleaded regular is 42 cents, from a low of $3.42 to a high of $3.79. ( -— ira.kantor@bostonherald.com )