So we all know how when you are in a group exp is increased by 10%, so with two people the same level you will get 1 half of 110% of the exp you would normally get. But how does this work with different levels/numbers of people in your group?

Do you get an extra bonus if you have all 5 slots filled? (vs say only haveing a group of 4)
How does it work with powerleveling? how much exp does 1 70 drain from 4 others?

Any information would be appreciated!