GMAT Sentence Correction (SC) | Re: The rules of differentiation allow a first-year calculus student to fi

Dear Mike,

I hope you are well.

I have 2 questions for choice B:

1 - Is the place of adverb 'easily' correct? Isn't better placed after 'could' or after 'be'? It may not be the case to reject the choice but it is subtle question to learn more.

2- I actually reject the sentence because of its awkward structure ' when you ........'. It seems to me more colloquial English that heavily used by people or non-native speaker when they insert a pronoun form no where. Am I correct in my analysis for