According to the U.S. Bureau of Labor Statistics, the unleaded gas prices for each month of the year in a large Texas city in 2013 were as follows below, rounded to the nearest hundredth of a dollar. January's price is on the far left, and the prices proceed in serial order month to month, with December's price on the far right.

3.30, 3.37, 3.53, 3.51, 3.49, 3.62, 3.59, 3.51, 3.58, 3.56, 3.57, 3.49

For these data, calculate the mode. Round to the nearest hundredths place. The mode is: