A main propulsion engine for a single prime mover plant has been in service for 24000 hours. The engine required maintenance at every 2000 hours for oil and filter changes (2 hours required), 4000 for pump maintenance (16 hours required), 10000 hours to change the cylinder heads (120 hours required) and at 20000 (660 hours required) for a major overhaul. Over the service life to date the engine has suffered a failure at 1500 hours (2 hours of down time), 5300 (64 hours of down time), 9200 (16 hours of down time), 14000 (48 hours of down time) and 18000 (240 hours of down time) hours.

Calculate the inherent Availability of the engine.