Que : At 31 October 2008, U conducted an impairment test on W and O, which are both cash-generating units in their own right. The recoverable amount of W was found to be $520 million ( excluding any effect on net assets of cash flow hedge ) and there had been no impairment of O.
Should I deduct impairment of $520 m from goodwill in W ?
In order to calculate the impairment in W you would need to compare the recoverable amount to the carrying value. If the carrying value is greater than the $520 million then there will be an impairment for the difference.
So, you need more information to calculate the impairment.