Chapter 5.5, Problem 7E

Reminder Round all the answers to two decimal places unless otherwise indicated.

Traffic Accidents The following table shows the rate $R$ of vehicular involvement in traffic accidents (per $100,000,000$ vehicle-miles) as a function of vehicular speed $s$, in miles per hour, for commercial vehicles driving at night on urban streets.

Speed s	Accident rate R
$20$	$1600$
$25$	$700$
$30$	$250$
$35$	$300$
$40$	$700$
$45$	$1300$

a. Use regression to find a quadratic model for the data.

b. Calculate $R\left(50\right)$ and explain what your answer means in practical terms.

c. At what speed is vehicular involvement in traffic accidents (for commercial vehicles driving at night on urban streets) at a minimum?