Yes, an off-topic question can be reopened, if the author edits it so that it falls within the site guidelines, which are linked in the Closed notice, and in Emilio's first comment above.
Your question currently looks like a "check my work" question, which is why David closed it. That close reason doesn't just apply to checking arithmetic, it also applies to "am I using the correct equation" questions.
I think it's valid to ask about equations if you express it in a conceptual way. That is, you need to ask why $W = mgh$ is the correct equation to calculate the work $W$ in lifting a mass $m$ a height of $h$ in a constant gravitational field with gravitational acceleration $g$.
However, it appears from your question that you don't actually have a conceptual difficulty with that equation. You're just bewildered that a little AA cell can do so much work. ;) So maybe your real conceptual question is "how can an AA cell store 14400 joules?"
But in any case, you need to change your question so that it's asking a conceptual question, as discussed in How do I ask homework questions on Physics Stack Exchange?
I see that you have edited your question since it was closed. That edit automatically sent it to the Reopen review queue. But your question still isn't a conceptual physics question, so it doesn't yet qualify for reopening. And asking about efficiency is turning it into an engineering question, rather than a pure physics question. Note that future edits will not send the question to the Reopen queue, but they will bump it to the top of the Active view of the main question page, which means that people will see it and possibly vote to reopen it, if they think it deserves to be reopened.
(BTW, Google is "smart" enough to answer things like
4 watt-hours in foot-pounds).