The question is:
Let $n$ be a positive integer and let $D$ be the subset of all rational numbers of the form $$\frac{a}{n^k}$$ with $a \in \mathbb{Z}$ and $k$ any positive integer. Show that $D$ is an integral domain whose quotient field is isomorphic to the field of rational numbers."
So to show that it is an integral domain, I used the theorem that every subring of a field is an integral domain. As for the quotient field, I'm not sure I understand how exactly to find it. I thought it was just some $a,b \in \mathbb{Q}$ such that $\frac{a}{n^k}\big/\frac{b}{n^k}$ is in $\mathbb{Q}$. Simplifying this would give $\frac{a}{b}$, which is the set rational numbers?
Any help would be appreciated.