Unilaterally reopening a question to answer it and then unilaterally closing it again is not an appropriate use of one's unilateral closing and reopening privileges. The privilege is not meant to give one a free pass to answer questions that should stay closed. This applies to both moderators and gold tag badge holders. A question should stay closed if it’s a duplicate, or stay open if it's not. In this case, the question is a duplicate and already has an answer in the duplicate target, so it is inappropriate and unnecessary to reopen it, answer it, and then re-close it.

Unilaterally reopening a question to answer it and then unilaterally closing it again is not an appropriate use of one's unilateral closing and reopening privileges. 

The privilege is not meant to give one a free pass to answer questions that should stay closed. This applies to both moderators and gold tag badge holders. A question should stay closed if it’s a duplicate, or stay open if it's not. 

In this case, the question is a duplicate and already has an answer in the duplicate target, so it was inappropriate and unnecessary to reopen it, answer it, and then re-close it.