You can't because Kant says you can't

The book I am reading at the moment is on Infinity theory - it sounds a bit tragic, granted - but it is damn interesting. [Dear god - whatever flakes your pastry - Ed] Although incredibly frustrating at times - with little gems like this to digest:

The act of using our minds and sense to apprehend the nature of true reality produces a change in its nature (and even if it doesn't, we can never know it doesn't).

Apparently that was Immanuel Kant's enduring contribution to philosophy - to be honest, I think Immanuel was being a bit of a Kant when he said it. It is basically the irrefutable premise, 'this is the way it is, and if you think it isn't, it's just because you don't know that it is. So there'. But if you ignore some of the more surreal concepts - other parts of the book throw up some interesting problems, so dear reader, here is yours for a Friday:

The guys walk into a hotel, each with $10 in their pocket. They book one room for $30 a night. A short while later a fax from headquarters directs the hotel to charge $25 a night. So the receptionist gives the bellhop $5 to take to the three guys sharing the room.

Since the bellhop never got a tip from them and because he can't split $5 three ways, he decides to pocket $2 and give the men each one dollar back. So each of the three guys has now spent $9 and the bellhop has $2, for a total of $29.

Where's the extra dollar?