The cost of a gallon of gas in Maine has inched up by more than a penny in the past week, yet still remains 8 cents below the national average. Price-monitoring website MaineGasPrices.com reports Tuesday that the average retail price of a gallon of gas in Maine is now $3.57. Nationally, prices are down more than 2 cents per gallon to an average of $3.65. In-state prices are now more than 12 cents lower than at the same time last year but almost 8 cents per gallon higher than a month ago. Maine prices are based on a survey of more than 1,200 gas stations across the state. A company analyst says prices are likely to fall in the near future.