1. The problem statement, all variables and given/known data In a circle city of radius 4 we have 18 cell phone power stations. Each station covers the area at distance within 6 from itself. Show that there are at least two stations that can transmit to at least five other stations. 2. Relevant equations 3. The attempt at a solution All I can say is that I'm pretty sure this is an application of the pigeonhole principle.