What is the major function of the OPEC?请用英语,

Representativs of OPEC Member Countries (Heads of Delegation) meet at the OPEC Conference to co-ordinate and unify their petroleum policies,in order to promote sability and harmony in the oil market.They are supported in this endeavour by the OPEC Secretariat,directed by the Board of Governors and run by the Secretary General,and by varioius bodies,in cluding the Economic Commission Board and the Ministerial Monitoring Sub-Committee.
The Member Countries consider the current oil market situation and forecasts of market fundamentals,such as economic growth rates and petroleum demand and supply scenarious.They then consider what changes.if any.they might make in their petroleum policies.For example,in previous Conferences the Member Countries have decided on several occasions to raise of lower their collective oil production.in order to maintain stable prices and steady supplies to consumers in the short,medium and long term.