The question is sound. My attention span is not.

I would hope those who are paid to hold the title of DBA are able to do these maths without too much difficulty.

I knew I had only a 1 in 7 chance of guessing correctly. I didn't care about getting the point, I just wanted to read the explanation. 🙂

As far as feedback on whether you should post the rest of the series: please do. Your posts are consistently high-quality and I'm sure you've put appreciable effort into your QotD series too. If I continue to incorrectly answer every on of them at least I know the ensuring discussions will be worthwhile reading.