Yep, you got it.
A blonde and an attorney sit in the train. The attorney decides to play the blonde off: "Excuse me, would you like to play? We ask ourselves mutually a question. The one who doesn't know the answer gives the other 5 Euro." The blonde rejects.
The attorney remains persistent and increases to her favour the employment: "Well ok, you receive 50 euro, I further only 5 euro for each not answered question." The blonde accepts that.
The attorney asks a long complicated juristical question. Because she does not know the answer to it, he gets like settled 5 Euro.
Then the blonde is on the move: "What has four legs when it moves up a mountain and three legs whn it comes down?" - the attorney considers for a long time and gives up finally and gives the blonde 50 Euro. She puts the note in and wants to leave the compartment. "One moment", calls the attorney, "and what is the answer?" Whereupon the blonde turns around and gives him mutely 5 Euro...