If a car had increased its average speed for a 210 mile journey by 5 mph, the journey would have been completed in one hour less. What was the original speed of the car for the journey?
Choose the correct choice from the following.
A) 20 mph
B) 10 mph
C) 30 mph
D) 40 mph
E) 60 mph
30 mph   30 mph
<result>C</result>
If a car had increased its average speed for a 210 mile journey by 5 mph, the journey would have been completed in one hour less. What was the original speed of the car for the journey?