Critical Reasoning

I have written this post to discuss a particular problem type (mostly cause and effect) mixed with negatives/positives + conditionals. This gets my head spinning, and I loose my focus and not able to apply a strategy I have. Example to explain the same.
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Kernland imposes a high tariff on the export of unprocessed cashew nuts in order to ensure that the nuts are sold to domestic processing plants. If the tariff were lifted and unprocessed cashews were sold at world market prices, more farmers could profit by growing cashews. However, since all the processing plants are in urban areas, removing the tariff would seriously hamper the government's effort to reduce urban unemployment over the next five years.

Which of the following, if true, most seriously weakens the argument?

A. Some of the by-products of processing cashews are used for manufacturing paints and plastics.
B. Other countries in which cashews are processed subsidize their processing plants.
C. More people in Kernland are engaged in farming cashews than in processing them.
D. Buying unprocessed cashews at lower than world market prices enables cashew processors in Kernland to sell processed nuts at competitive prices.
E. A lack of profitable crops is driving an increasing number of small farmers in Kernland off their land and into the cities.

OA is E and I have absolutely no issues in dealing with D, a strengthener, and E.
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This questions has clearly stated conclusion so it is easy to identify the same. The problem lies with the fact that we have causal relation ship containing negative elemtns both sides:

Removing the tarrif -> hamper the goverment plan (meant to improve employment in urban areas)
In general cause and effect question (X -> Y) , we have standards way to weaken:

1. Not X -> Y 2. X -> NOT Y 3. Z -> Y 4 Y -> X so far so good.

Problem begins when X and Y do contain some negative elements as in the given example and questions asks again to weaken them.At this stage, i can't get clear translation in my head so looking for a robust way to attack.In the given question:
X is removing tax: Y is hampers the plan

Before proceeding to answer choices, what should be paraphrased in my mind or at least when I read the anser choice, i should be able to quickly answer?

so X -> Y ; can i say NOT X -> NOT Y ? that means Not removing Tax - > does not hamper the plan..or in other words:

Keep the tarrif -> good for unemployment plan; now I can use normal cause and effect arugment again as these are my new SIMPLIFIED X and Y?

And Can i extend it further to cases such as NOT X -> Y; weaken question.

So by negating both sides we can also say X -> Not Y; and now we can start looking and see which ever case is given.

And is this strategy robus and can be applied in all cases ?

thank you so much for detailed insight on this.