Hello, I originally posted this in the comments under the question but the more I look at it I'm second guessing if my reasoning is correct. I've pasted it here with a couple alterations because I accidentally put "understand" instead of "know" in the other post. It got me to the correct answer but could someone please confirm if my reasoning is correct and if not, where I went wrong. Thank you.
59.3.19
Premises:
A := Understanding a word
B := Knowing its dictionary definition
C := Understanding the words that occur in the definition
(A →B) → (A → C)
Premises: we have an instance of people (e.g., babies) who don’t understand the words that occur in the definition.
==> C
Necessary failed, contrapose back.
==> (A →B)
which is equivalent to
A and B
In other words, it could be the case that people (e.g., babies) understand the words they’re saying even if they don’t know the word's dictionary definition.
Which matches AC (E).
In this case it wouldn't really make sense I don't think but to better answer your question I'll attempt to explain it - to negate an exclusive or you're saying that it's not the case that either of those conditions will happen alone. If you watch J.Y.'s truth table video on it it might make more sense but you're basically saying the only two cases that Anne will have after the negation are the case where she neither takes a leave of absence from Techno and returns in a year nor quits her job at Techno (which I diagrammed above). Or the second case, where you're saying that she will do both of those things, i.e., Anne will take a leave absence from Techno and return in a year and she'll also quit her job at Techno. Which is why I'm questioning whether it makes sense to even consider the second case lol. But that's how the logic works out.