On a trip, a car traveled $80$ miles in an hour and a half, then was stopped in traffic for $30$ minutes, then traveled $100$ miles during the next $2$ hours.  What was the car's average speed in miles per hour for the $4$-hour trip?
$\text{(A)}\ 45 \qquad \text{(B)}\ 50 \qquad \text{(C)}\ 60 \qquad \text{(D)}\ 75 \qquad \text{(E)}\ 90$
The average speed is given by the total distance traveled divided by the total time traveled.
\[\frac{80+0+100}{4} = \boxed{\text{(\textbf{A})}\ 45}\]