LR Question 16 Explanation, by LSATHacks
QUESTION TEXT: Engineer: Thermophotovoltaic generators are devices that convert…
QUESTION TYPE: Necessary Assumption
CONCLUSION: Thermovoltaic generators could save money if steels plants were able to use them to convert heat to energy.
REASONING: Thermovoltaic generators convert heat to energy. Steel manufacturing produces a lot of heat.
ANALYSIS: This is a tricky argument. You have to read carefully. It’s easy to think “maybe steel plants won’t be able to use thermovoltaic generators!”.
But that doesn’t matter. The argument is about what happens if steel plants are able to feed energy to generators. Whether steel plants can do so isn’t an issue, since we’re talking about what would happen in a hypothetical situation.
The actual flaw is different. The argument has shown that feeding heat to generators would produce electricity, which saves money. But, the argument didn’t say what it costs to feed the heat to generators. It could be so expensive to feed heat to generators that the costs outweigh the savings.
___________
- The argument only said that thermovoltaic generators would be a good way of using the heat. It doesn’t matter if there are even better ways to use the heat.
- It doesn’t matter whether we can currently feed heat to thermovoltaic generators. The argument is only talking about what would happen in a hypothetical situation where we are able to feed heat to the generators.
- CORRECT. If the energy savings don’t cover the cost of installation and use of the generators, then steel plants wouldn’t save money by using thermovoltaic generators.
- It doesn’t matter if electricity is a primary source of energy. It only matters that electricity is a source of energy. As long as electricity is used, then thermovoltaic generators could offset energy bills.
- The argument only said that thermovoltaic generators would be a way of saving money. It doesn’t matter whether they’re the only way. This is similar to A.
It’s frustrating how close answer choices B and C are in terms of being necessary assumptions. The problem I see with C is that it does not indicate the running costs will be covered, it specifically states “amount steel-manufacturing plants would save on their electric bills by feeding heat into thermophotovoltaic generations would be sufficient to cover the cost of PURCHASING and INSTALLING those generators”. There is no mention of the ongoing running cost, which in my opinion makes the answer choice open to interpretation. If the running cost is not accounted for in the operation of the generators then the savings might be eroded to a point where they are non existent.
If answer choice B is not true, and conversion of at least some heat into electricity is not possible, then the entire argument is invalid – no conversion = no electricity bill reduction = no saving of money.
I see why they went with C, as it directly address a component of the argument – cost consideration; but I still feel it is too open to interpretation to be included in a necessary assumption question type.
You raise a valid point on C. But it goes in the other direction. So, let’s say to be profitable, the company would need to cover:
$10,000,000 install cost
$1,000,000 annual operating cost
To profit they need to cover both. But if you negate C, it says the electrical bill savings don’t cover the first part. If they don’t cover the first part then clearly they can’t cover both the first and second parts. So your objection makes C and even better answer.
B doesn’t matter because the argument was hypothetical. It’s like if I said “If you go to medical school you’ll become a doctor” and you say “That’s not true, I currently can’t get into medical school”. It doesn’t matter whether you are in medical school or could get there now. We’re only discussing what happens IF you go to medical school.
Note: This is an old comment but I wanted to clarify the point.