Why would OPEC want to meet with non-OPEC countries to implement a deal OPEC made to cut its output?

http://www.reuters.com/article/us-oil-opec-algeria-idUSKCN1252CN

Questions:

1. What happens to the price of oil if OPEC cuts output and non-OPEC keeps output constant?
2. When are profits higher for OPEC, when non-OPEC countries keep output constant after the cut or when non-OPEC countries increase output after the cut?
3. When are profits higher for non-OPEC, when non-OPEC countries keep output constant after the cut or when non-OPEC countries increase output after the cut?