A company with long–outstanding bills owed by its customers can assign those bills to a collection agency that pays t...

Courtney on April 12, 2021

Why is B incorrect?

I see why A is correct, but I need help seeing why B is incorrect. Thanks!

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Kyle on April 26, 2021

As a caveat, I'm just another LSAT studier, so I'm not the highest authority with regards to answer choice explanations.

This question has a strengthen with necessary premise stem, which means we have to identify whether a given answer choice strengthens the argument, and if it does, then we have to negate it and treat the negation as a sufficient condition for the conclusion. The correct answer will be an answer choice that strengthens the argument, but also renders the conclusion wrong when the answer choice is negated. Hopefully that makes sense.

With that in mind, I believe answer choice B is apparently incorrect after taking it's negation: the cost to a company of pursuing its debtors on its own for payment of long–outstanding bills does exceed 15 percent of the total amount of those bills. This negation is simply not exclusive enough to make the conclusion wrong, thus it is not a necessary premise.

For the sake of argument, let's assume that the cost of pursuing these debtors amounts to 16% of the total amount of the bills, and let's also assume that they collected 100% of the total amount of the bill. This would mean that their net profit (for lack of a better word) would be 84%. What they collect themselves would therefore be far greater than what they would collect through an agency, which would give them 15% of the total amount of the bill, assuming they have a 100% success rate. In other words, this one scenario would not make the conclusion inaccurate.

Undoubtedly, using answer choice B as a premise, a scenario could be made in which this conclusion is rendered incorrect, but a correct answer choice for a strengthen with necessary premise, is one that will always render the conclusion erroneous when the premise is negated.

Hope this makes sense. Sorry for the extended response, but I just wanted to be as thorough as possible. Good luck!