My mathematical mind

I've assigned my first set of homework problems. The first email I got from a student about it was very respectful and very relevant (a word could be interpreted two ways- my bad). The second came asking if we could meet today. It came 20 minutes after my office hours were over. hmph.
Ok fine, I will be in my office all day anyways. The third. Oh, the third. The third did not ask a question. The third was writing to inform me that the problem was written wrong because it didn't work correctly when they worked it out. The fourth was the student from the third saying there is another problem that I wrote wrong, based on their calculations.

Really? I admit that I am obviously not infallible. I messed up and didn't use as specific a word as I could have in a different problem and I totally get that. But writing two problems completely wrong? It didn't occur to you that you might be doing the problems wrong?
No? Not at all?

Of course not.