How much should I charge for this?

[rachmaninoff_forever]

Okay so my gf had this Arabic teacher in her undergrad and now her teacher is teaching at university of Chicago and she wants me to play some Arabic songs for a presentation on Arabic music.  (I don't think Ima be doing a lecture this time). 

It's about 20 minutes.

And they asked me how much I should charge.

[themeandvariation]

It depends.. Have you heard and or seen the music?  If so, Would it be difficult to learn?
Are you a good sight reader and quick study?  20 minutes Can be all long time - and if it is difficult material, and I would charge more - if that is the case... But if you can get it in a couple of practice sessions, I would charge somewhere around $200 ...
in special cases (circumstances)- and if i like the music - maybe go as low as $150...but no lower.