Answer
(a) $y=463.67x + 6312$
(b) $8166.68\ dollars$, overestimated 96.68 dollars.
Work Step by Step
(a) With two points $(0, 6312)$ and $(3, 7703)$, we can find the equation as $y-6312=\frac{7703-6312}{3-0}(x-0)$ or $y=\frac{1391}{3}x+6312\approx463.67x + 6312$
(b) For year 2013, $x=4$, we have $y=463.67(4) + 6312=8166.68\ dollars$, this number overestimated the actual value of 8070 by 96.68 dollars.
