After 6 months, ammount left to pay = $1,840.34
On the seventh month, he payed of the debt with the interest (for one month).
Amount paid off at the seventh month = 1840.34(1 + 0.09/12) = 1840.34(1.0075) = 1854.14
Amount to have paid in the remaining 6 months = 314.83 x 6 = 1888.98
Amount saved = 1888.98 - 1854.14 = $34.84