We have a case of grammatical correctness here so we must be attentive to every detail because it would matter as we try to get the best of the options.

Option A - INCORRECT.
This in fact is a grammatically wrong statement. Retools is a poor choice of word to use in terms of the tense formation. Another important point is the lifting of the paragraph from the question without any difference.

Option B - INCORRECT.
Here, we have the same situation at hand. Instead of using ''Retools'' the present tense could have been much better i.e. ''retool'' since it's explaining what's happening presently.

Option C - CORRECT.
Here, there is a basis for the use of past tense of ''retool'' i.e. ''retooled''. The first case was when the company ''Hired'' the marketing firm and the second action taken was the ''retooling'' of it's factory. So, the past tense ''retooled'' fits perfectly because the precedence had been set.

Option D - INCORRECT.
It's not a futuristic action, it has already been done so it's inapplicable here to use the future tense ''will''. it negates the intention of the author.

Option E - INCORRECT.
It would have been logical if the past tense of ''produce'' has been used i.e. ''Produced'' because it has the potential to replace the verb ''retool'' in the context it's been used.