a/an vs the

Can I use two articles "a" in the following sentence or should I use two articles "the"?

It's a right answer, but not a complete one.



P.S.
I use an indefinite article twice here, because I belive "right aswer" is not single in the given specific case.
But I should use a definite article if "right answer" is single. And in that case I will say: "It's the right answer."
Is my reasoning correct?

Thank you!