A north-south highway intersects an east-west highway at point P. A vehicle crosses P at 1:00 p.m., travelling east at a onstant speed of 60 km/h. At the same instant, another vehicle is 5 km north of P, travelling south at 80 km/h. Find the time when the two vehicles are closest to each other and the distance between them at this time.

Any help would be greatly appreciated!