At 2:00 pm boat K is 25 km north of boat L. If boat K is sailing 5 km/h west and boat L is sailing north at 20 km/h, what is the rate at which the distance between the two boats in changing at 2:30?

I'm pretty sure that you have to either find the angular or linear speed. That's as much as I could tell you. I'm sorry. Could you possibly help me with my question? It's on the current questions page.