Based on the original version of the question (see the history), it was very natural to vote to close this question "as homework," which I did, but then I changed my mind:

I voted to close, but on reflection I think it was largely because of the imperative structure of the question (this immediately sets of the homework flag in most of our minds). The universal example is not finite unless r=s=2, and after a few minutes thought it's not obvious to me how to build G. This is a precise and nonobvious mathematical question, so I'm going to edit it and encourage others to vote to reopen it. I don't really care if this is homework.

I feel like the edit did not change the actual content of the question, and if the question had been posed this way in the first place, I wouldn't expect it to be closed.

Agree? Disagree?