In 1991 the average family income was about 39000, and in 2011 it was about 66820.

Let
x
=
0
represent 1991,
x
=
1
represent 1992, and so on. Find values for
a
and
b
(rounded to one decimal place if necessary) so that
f
(
x
)
=
a
x
+
b
models the data
a
=


b
=



What was the average family income in 2006?