I'm in grade 12 and this was given on a test and I had no clue how to solve it (it was a bonus question)

If two men are running away from each other at 45 degrees and man1 is running at 12 km/h and man2 is running at 10 km/h; How fast are they moving apart at 2.5 hours?

So I first made a drawing:

Is that correct?

I have no clue how to come up with an equation with respect to time.

Please help