Chapter 2 - Graphs and Functions - 2.5 Equations of Lines and Linear Models - 2.5 Exercises - Page 246: 67

(a) $C=0.6516I+2253$ (b) $0.6516$

(a) Given points $(12026,10089)$ and $(14167,11484)$, assume $C=mI+b$, we have $m=\frac{11484-10089}{1416712026}\approx0.6516$ and $b=C-mI=10089-0.6516(12026)\approx2253$, thus we have $C=0.6516I+2253$ (b) The slope, or the marginal propensity to consume, can be found as $0.6516$ for the United States from 2009–2013.