Hi blue - thanks for the question! I've got this drill question on page 9-60 in my copy of the book (which is likely more recent), so just FYI for anyone else who happens to read this
As to whether it's possible that a charity receives no toys, I would say no from the scenario ("toys are given to four charities" to me implies that each receives at least one), and certainly once we explore the rules a bit it becomes impossible for any charity to have zero: charity 2 has at least one, charity 3 has more than charity 2 (so at least two), and charity 4 is one less than charity 3 (so charity 4 gets a minimum of one). And of course charity 1 gets three times as many as charity 2, so charity 1 gets at least three toys.
Without those rules if I was still uncertain about a zero-toy option I'd quickly glance at the questions and answers and see if the situation ever arises. If it's shown as possible in a question or answer choice then you know it's allowed, and if it doesn't ever come up then chances are it's not possible (or at least won't matter).
I hope that helps!
Jon Denning
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