OSLO, Oct 12 (Reuters) - Prosafe :
* Says contract extension for Safe Astoria at North Rankin B
* Says the value of the exercised option is approximately USD 5.7 million
(Reporting by Oslo newsroom) ((gwladys.fouche@thomsonreuters.com; +47 22 93 69 77; Reuters messaging: gwladys.fouche.reuters.com@reuters.net))