Chapter 12.3, Problem 81E

Oil Imports from Mexico Daily oil production in Mexico and daily U.S. oil imports from Mexico during 2009–2013 can be approximated by

$\begin{array}{l}P\left(t\right)=3.1-0.014t\text{ million barrels }\left(9\le t\le 13\right)\\ I\left(t\right)=1.7-0.063t\text{ million barrels }\left(9\le t\le 13\right)\end{array}$, wheret is time in years since the start of 2000.

Graph the function $I\left(t\right)/P\left(t\right)$ andits derivative. Is the graph of $I\left(t\right)/P\left(t\right)$ concaveup or concave down? The concavity of $I\left(t\right)/P\left(t\right)$ tellsyou that

(A) the percentage of oil produced in Mexico that was exported to the United States was decreasing.

(B) the percentage of oil produced in Mexico that was not exported to the United States was increasing.

(C) the percentage of oil produced in Mexico that was exported to the United States was decreasing at a slower rate.

(D) the percentage of oil produced in Mexico that was exported to the United States was decreasing at a faster rate.