Orc race powers

[mblede]

Hello people!

I've just bought Munchkin 2, and I have a question about the powers of the orc race.

Where it says "When an orc fighting alone defeats a monster by more than 10, he goes up an extra level".
Here are my questions about it:

- does the orc have to fight a monster over than level 10? or the orc level + 10, eg. orc is level 5 and the monster is level 15? (I'm not an English native speaker, so this might be a problem of understanding)
- can it be the winning level, eg. from level 8 to 10?
- should the bonuses be taken in account to calculate the difference?

Many thanks to who will answer me :)