Answer
(a) $-8.17\ k$ mobile homes/year
(b) See explanations.
Work Step by Step
(a)
Step 1. Identify the needed data: $x_1=2003, f(x_1)=138\ k$ and $x_2=2013, f(x_2)=56.3\ k$
Step 2. Use the formula for the average rate of change: $m=\frac{f(x_2)-f(x_1)}{x_2-x_1}$, we have $m=\frac{56.3-138}{2013-2003}\approx-8.17\ k$ mobile homes/year
(b) The negative slope means that the number of mobile homes decreased by an average of 8.17 k mobile homes/year during this time.
