Try here
http://www.eurocopter.com/ec120/
The technical data will tell you payload/range. You just have to work out what you expect your EEW/BOW to be.
The 120 is about the same as a 206B3. Both probably perform equally as badly in the hands of the inexperienced. Normally you can't fill the seats and the tanks in either of them.
It does what it says on the label.