Sweet revenge

A guy is looking for a place to sit in a crowded library.

He asked a girl in a university library: "Do you mind if I sit beside
you?

The girl replied with a loud voice: "I DON'T WANT TO SPEND THE NIGHT
WITH YOU!"

All the students in the library started staring at the guy; he was
truly embarrassed and moved to another table.
After a couple of minutes, the girl walked quietly to the guy's table
and said with a laugh, "I study psychology, and I know what a man is
thinking. I guess you felt embarrassed, right?
The guy then responded with a loud voice: £500 FOR ONE NIGHT? . . .
THAT'S TOO MUCH!
All the people in the library looked at the girl in shock.

The guy whispered in her ear: "I study law, and I know how to screw
people".