It's grammatically OK, but not at all natural. The natural answer is: "Yes, I do". By the way "Can I so answer?" is not normal English, either - it sounds like something out of the 17th century! Instead, you could say "Can I answer like this?" or "Is this a correct answer?".

Yes, I do. sounds better.

The best answer is simply 'Yes' or 'Yes, I do'

That answer would be fine, yes.