The National Highway Traffic Safety Administration reported the relative speed (rounded to the nearest $5 \mathrm{mph}$ ) of automobiles involved in accidents one year. The percentages at different speeds were

$20 \mathrm{mph}$ or less	$2.0 %$
25 or $30 \mathrm{mph}$	$29.7 %$
35 or $40 \mathrm{mph}$	$30.4 %$
45 or $50 \mathrm{mph}$	$16.5 %$
$55 \mathrm{mph}$	$19.2 %$
60 or $65 \mathrm{mph}$	$2.2 %$

(a) From these data, can we conclude that it is safe to drive at high speeds? Why or why not?

(b) Why do most accidents occur in the 35 or $40 \mathrm{mph}$ and in the 25 or $30 \mathrm{mph}$ ranges?

(c) Construct a density histogram using the endpoints $0,22.5,32.5,42.5,52.5,57.5,67.5$ for the intervals.