Train Probability Puzzle

The probability of observing a train in 30 minutes on a track is 665/729. What is the probability of observing a train in 5 minutes ?

Hint : Shoot for an elegant solution.

Troyis Game

I came across this game called Troyis. Being a theoretician, whenever I come across a new game, the first question that comes to my mind is "What is its complexity ?". Here is the decision version of Troyis :

• TROYIS : Given an instance of Troyis, can you paint all the white cells in <= k clicks ?

Here is a puzzle : Prove (or disprove) that TROYIS is NP-complete.