The only way that bookstores can profitably sell books at below-market prices is to get the books at a discount from ...

SamA September 25, 2019

Hello @Neela,

I'll diagram this problem we will see if that answers your question.

Premise: The only way that bookstores can profitably sell books at below-market prices (BMP) is to get a publisher discount (PD).

BMP - - - - - - - - - -> PD

Premise: Unless bookstores generate high sales volume (HSV), they cannot get publisher discounts (PD).

BMP - - - - - - - - - - -> PD - - - - - - - -> HSV

Do you see how our chain is growing? If either of these necessary conditions fail, then the bookstore cannot profitably sell at below market prices.

Premise: There are only two ways to generate high sales volume. The bookstore can cater to mass tastes (CMT) or have exclusive access to a large specialized market (LSM).

BMP - - - - - - - - - - -> PD - - - - - - - -> HSV - - - - - > CMT or LSM

You are welcome to diagram however you feel most comfortable, but I just write the word "or". This indicates to me that we don't need both of these conditions, but we need at least one of them.

The question stem then removes one of these conditions (CMT) making us entirely dependent on (LSM).

BMP - - - - - - - - - - -> PD - - - - - - - -> HSV - - - - - - - > LSM

Now, we can see why answer choice D cannot be true. It eliminates the large specialized market (LSM), making it impossible for the store to profitably sell books at below-market prices.

I hope this didn't confuse you further, feel free to @ me if you have more questions.

Anna20 May 14, 2020

Hi @SamA - thanks so much for the above. I would be grateful if you could kindly elaborate as to why this is read as removing CMT from the question stem, rather than: not CMT and not LSM --> not HSV - i.e. as the contrapositive, which then doesn't have one of the variables and therefore, you can't have HSV?

How do you know how to read this question? Grateful if you could please let me know what I'm missing? Thanks so much!

Anna20 May 16, 2020

Apologies, grateful if I could kindly follow up on this question? Many thanks in advance and much appreciated.

Anna20 May 29, 2020

Please can I follow up on this. Thank you.

Anna20 June 2, 2020

Please can I follow up on this. Thank you!

AnthonyH June 19, 2020

Hey, I have a similar question. My understanding was that we could not assume the existence of LSM simply because No CMT. Without the explicit premise to exclude both (No CMT & No LSM), how can eliminate the contrapositive argument with certainty?

Did @Sam or someone ever respond to the request to clarify?

Brett-Lindsay July 4, 2020

Thanks Sam! I love that way of looking at it.

I'll try to explain my understanding of the concept with coffee. If a person is into black coffee, but they like it a bit sweet, they'd add a sweetener. Let's say that they have only 2 choices: sugar or honey.

You could set up a S/N conditional:

C --> S or H (Coffee --> Sugar OR Honey. Remember, we don't need both)

Taking the contrapositive, we'd get

not S and not H --> not C

Imagine that the coffee shop happens to have just run out of honey, we can take honey out of the equation:

C --> S
not S --> not C

As there's already no honey, now, if there's suddenly no sugar, I can't have my coffee.

This imaginary (or not) situation is very similar to that in the question.

The question prompt ruled out one of our A or B requirements:

"...a bookstore does not cater to mass tastes"

This would mean we could just remove it from consideration as in the coffee example.

Hope this explanation helps.