Except as provided in subsection (i), if gasoline is used in an off-highway business use, the Secretary shall pay (without interest) to the ultimate purchaser of such gasoline an amount equal to the amount determined by multiplying the number of gallons so used by the rate at which tax was imposed on such gasoline under section
4081. Except as provided in paragraph (2) of subsection (f) of this section, in the case of gasoline used as a fuel in an aircraft, the Secretary shall pay (without interest) to the ultimate purchaser of such gasoline an amount equal to the amount determined by multiplying the number of gallons of gasoline so used by the rate at which tax was imposed on such gasoline under section
4081.