Question : A North-South highway intersects an East-West highway at point P. An

automobile crosses P at 10:00 am, traveling east at a constant speed of 20 km/h.

A car north of P, twenty minutes later passes that same point, traveling south at 60

km/h. Find the approximate the minimum distance between the automobiles.

Answer: 6.3 km

I keep getting 7.8 km as my answer- don't know if I'm setting up the equations wrong or if the answer is wrong. Please help~ and thanks in advance