The cost of a gallon of gas in Maine has dropped nearly two cents in the past week to an average of $3.56. Price-monitoring website MaineGasPrices.com reports Monday that even though the average retail cost of gasoline continues to fall in Maine, it is still not falling as fast as it is nationally. The national average fell nearly four cents in the past week to an average of $3.39, 17 cents lower than in Maine. Maine prices are seven cents lower per gallon than a month ago but more than 19 cents higher than at the same time last year. A company analyst says prices are expected to continue to fall gradually through Christmas.