@vitamind The answers at the duplicate link do answer the question, but it's also a "no clue" question and asking to show something which isn't correct, which qualifies it for closure for context or needs details/clarity, respectively. Tough choice! I think I'm going to vote to close for context, but I wouldn't be unhappy with any of the three options.
PSQ But can someone check if the answer is correct? In my opinion you can't define the question since there's no uniform probability measure on the real line.
@TeresaLisbon Don't think any amount of editing can make it look better with that kind of attempt from the asker. It's just like the other day where a web search would have yielded the answer, but some people would rather answer the same thing over and over again (even if they have answered it before).
The answer to this would become correct, if the range where the pen can fall is restricted to a finite interval. I wonder however whether this question should have been answered at all.
@Peter I believe it's restricted to fall in a line of length L, which means that the uniform probability measure is definable (I made an error while posting this question earlier, and should have noticed this). Then again that's not clear, and it's not clear to OP that the problem is even definable. But that, of course, is why the question shouldn't have been answered.
@Peter Correct. My bigger problem is the answer, though. WHY would I want to put the Lambert and Gamma functions with harmonic numbers into a context where I'm basically dealing with numbers? The problem is the answerer converting the question into one they like, then answering that question, and claiming rep for it.
That's the worst kind of desperation : when you want to answer a question so much that you are ready to tweak it then and there, and write down anything you can in the hope OP can understand (OP must be thinking, what is the Lambert function? surely, this is an OP that has issues in tracking multiplication!)
@Peter I saw that, it has two delete votes (the answer); I already downvoted and helped close the question. One more downvote on the question, and we can open it for deletion.