It’s unanswerable because your answer changes the probability.
If you think you have a one in four chance at random, it’s 25% - except there are two 25%s, so the chances are 50%.
But you only have a 25% chance of picking the 50%, so it’s back to 25%.
If it’s impossible, the chances are 0%, right? Nope, because you have a 25% chance of picking 0%…