Answer
$y=-t+11.7$
Projected in 3rd quarter of 2011:$\quad {{\epsilon}}\ 8.7$ billion
Work Step by Step
The regression line is
$\qquad y=mx+b$,
where $m$ and $b$ are computed as follows.
$m=\displaystyle \frac{n(\sum xy)-(\sum x)(\sum y)}{n(\sum x^{2})-(\sum x)^{2}}\qquad b=\frac{\sum y-m(\sum x)}{n},$
$n=$ number of data points.
$\left[\begin{array}{lllll}
& t & y & ty & t^{2}\\
& & & & \\
\hline & 0 & 12 & 0 & 0\\
& 1 & 10 & 10 & 1\\
& 2 & 10 & 20 & 4\\
\hline & & & & \\
\sum & 3 & 32 & 30 & 5\\
& & & &
\end{array}\right]$
$m=\displaystyle \frac{3(30)-(3)(32)}{3(5)-(3)^{2}}=\frac{-6}{6}=-1$
$b=\displaystyle \frac{32-(-1)(3)}{3}=\frac{35}{3}\approx 11.7$
$y=-t+11.7$
In the third quarter of 2011, $ t=3$ and we have
$y=-3+11.7=8.7$
