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J.K. Rowling could have chosen any nonnegative integers {n,p,q} for {p,q} being relatively prime, p<q and q not equaling 0, for platform n p/q (she could have technically chosen a nonnegative irrational number, but let's forget that idea for now). So why did she choose n=9, p=3, and q=4?
I have n...