John and Amanda stand at opposite ends of a straight road and start running towards each other at the same moment. Their rates are randomly selected in advance so that John runs at a constant rate of 3, 4, 5, or 6 miles per hour and Amanda runs at a constant rate of 4, 5, 6, or 7 miles per hour. What is the probability that John has traveled farther than Amanda by the time they meet?

(A) 3/16
(B) 5/16
(C) 3/8
(D) 1/2
(E) 13/16

[spoiler]OA=A[/spoiler]

Source: Manhattan GMAT