Q10

[09weie]

In the diagram explanation provided, they don't make the inference that since P is in, H--L. What's the reason for that? It's where I began. I'm also lost about how the author came to the conclusion for answer choice A that "if H goes first, P goes last." Where did that come from? Am I totally missing something?

[ohthatpatrick]

You're totally right on that first point. The explanation confusingly says that we can infer very little from P being in spot 5, but we can certainly apply the final rule and know that H and L are both included with all H before all L.

The comment about (A) is based on the 3rd rule. "If H is first, then P is last".

If I were explaining Q10, I would basically have this on my page

____ ____ ____ ____ P ____ (H - L)
~H ~L

I'm just saying no-H in 1 because of the contrapositive of rule 3. No L in spot 2, because the earliest we could put H down is 2.

That up front work kills off (A) and (D), but the others still involve some plug and chug or at least some mental consideration of how that would work.