A man was looking for a place to sit in a  crowded university library.
He asked a girl: "Do you mind if I sit beside you?"
The girl replied, in a loud voice "NO, I DON'T WANT TO SPEND THE NIGHT WITH YOU!"
All the people in the library started staring  at the man, who was  deeply
embarrassed and moved to another table.

After a couple of minutes, the girl walked  quietly to the man's table  and
said with a laugh: "I study  psychology, and I know what a man is  thinking;
I bet you felt embarrassed, right? 
"The man responded in a loud voice: "$500 FOR ONE NIGHT? ..... I`M NOT
PAYING YOU THAT MUCH!"

All the people in the library looked at the girl in shock.
The man whispered to her: "I study law and I know how  to screw people". 

Aussie Paul.