Akpors and The professor

A Prof and Akpors was seating next to each other in a
long flight.

Prof said to Akpors: lets play a game, I will ask you a question and if you didn't get the answer, you will pay me $50,
and if u ask me a question and I didn't get the answer, I
will pay you $5000.

The Prof started :What is the distance from the earth to the moon?

Akpors doesn't say a word, he reaches his pocket and pulled
out a $50 and gave him.

Now is akpors turn to ask,
He said: what goes up in the hill with 3 legs and comes down with 5 legs?
The Prof thought for a long time,searches the net, and asked all his smart friends
but couldn't get the answer.
He reaches his pocket and pulled out a $5000 and gave it akpors.

Prof got mad and asked Akpors: well, what the hell goes up the hill with 3legs and comes down with 5 legs?.

Akpors just deep into his pocket and gave Prof $50 and
said: I don't know also.