Question 111
A space station consists of 25 chambers, and every two chambers are connected by a tunnel. There are a total of 50 main tunnels that can be used in both directions, the rest are all one-way tunnels. A group of four chambers is said to be connected if one can get from any of these chambers to any other using only the six tunnels that connect these chambers to each other. Determine the largest possible number of connected groups of four.