* Part of the tax is a 17.5-cent flat tax per gallon.
* Add either 3.5 cents per gallon, or 7 percent of the average wholesale price for a designated six-month period, whichever is greater.
In this case, it's the six-month period that ended Sept. 30. The average wholesale price was $1.7755, and the tax is 12.4 cents.
* Total tax, beginning Jan. 1: 29.9 cents per gallon.