Two cars start at the same point and travel inopposite directions.  If ... ...

Two cars start at the same point and travel in opposite directions.  If one car travels at 45 miles per hour and the other at 60 miles per hour, how much time will pass before they are 210 miles apart?
(A)   .5 hours
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Nova Press: Set S - Word Problems