John started driving on a highway at a constant speed of R miles per hour at 13:00. Then, 2 hours later, Tom started driving on the same highway at a constant speed of 2R miles per hour at 15:00. If both drivers maintained their speed, how many miles had John driven on the highway when Tom caught up with John?	Choose the correct choice from the following choices:
A) 2R
B) 3R
C) 4R
D) 5R
E) 6R
In 2 hours, John drove 2R miles.   Tom can catch John at a rate of 2R - R = R miles per hour.   The time it takes Tom to catch John is 2R / R = 2 hours.   In 2 hours, John can drive another 2R miles for a total of 4R miles.   The answer is 4R.
<result>C</result>
John started driving on a highway at a constant speed of R miles per hour at 13:00. Then, 2 hours later, Tom started driving on the same highway at a constant speed of 2R miles per hour at 15:00. If both drivers maintained their speed, how many miles had John driven on the highway when Tom caught up with John?