How fast must Michael be running and how far? (This is basically the same as those "train" questions.)

Let’s say Kelly is running a 3-mile loop at her favorite local park, and she sees her friend Michael running the other direction, they pass each other 3 times by the time Kelly finishes running.

If Kelly only does the loop one time, and it takes her about 40 minutes, how fast must Michael be going? Kelly does not know where Michael started his loop, so she does not know exactly how far he has run, but she thinks he must have run further than she has. What’s the minimum number of miles Michael must have run?

No, this isn’t my homework! It’s something I’ve been thinking about, and I tried to phrase it in a way that would be easy to understand.

Thanks!