Whenever you're asked to support a particular conclusion, you want to think about what information is missing - what logical gaps exist - between the premises and the conclusion.
Premise:
New tires cost more than old tires, even though they weigh less.
Conclusion we want to support:
New tires will nonetheless be economically beneficial
Whenever you're asked to consider economic benefit on CR, we want to consider that profit = revenue - costs. Since it's unlikely that tires will affect the revenue of the company, we probably want to consider the various costs involved. We're given one piece of information about cost as it relates to tires - how much they cost to produce. But is that the only cost involved? What about how often we have to purchase them, how much they cost to maintain, etc, etc.
Logical Gap:
Is there some other way that the new tires could lower costs?
A. The fact that old tires will go out of production in 10 years does not mean that new ones are more cost-effective in the present.
B. If the tires weigh less, the whole truck will weigh less (all else being equal), so fuel costs will be lower on the new tires. CORRECT
C. This would weaken - it's an increased cost for new tires
D. The fact that it's designed for extreme conditions does not mean that it will be more cost-effective in real-world conditions.
E. This doesn't weaken the conclusion, but it doesn't exactly strengthen, either. It's saying - there won't be any increase in training or equipment costs. But to support our conclusion, we need to know that there's a decrease in some other cost.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
