I reckon J.Darren is correct, the problem is that everybody bar him has misinterpreted the question. The question states that "At 0600 hours the liner, which is 90 km from a lifeboat and on a bearing of 315 from the lifeboat...". All the other answers seem to assume that the liner is on a bearing of 315 from the lifeboat at 0730 hours, and not at 0600 hours.
cooldude, you've just made a computation error - everything is correct up to the bit when you somehow say that A is 133.75 km.