Don’t try to impress the employer with an overly high number of articles. It all depends on the word count of articles.
As an example, one can write more 500 word articles as compared to 2000 words detail articles. So keep the number of articles you can deliver per week to reasonable.
Content writing is a creative job.
On the other hand, such questions are meant to get you carried away. You may even promise more than what you can deliver. Be self-aware. Know your skill sets and level of competence.