Question 89
A surveillance service will be installed in a park in the form of a network of stations. The stations must be connected by telephone lines, so that any of the stations can communicate with all the others, either through a direct connection or through at most another station. Each station can be connected directly by one cable to a maximum of 3 other stations. The diagram shows an example of such a network connecting 7 stations. What is the largest number of stations that can be connected in this way? 