Answer:
In the first sentence, 'each week' modifies the verb 'buying' and suggests that if Marsha wishes to buy a new bike, she will require to save $10 every week. While in the second sentence, 'each week' modifies 'need' and suggests that if she is willing to buy a new bike every week, she will have to save $10. Thus, the first sentence conveys the meaning logically because buying a bike for $10 is unsound and irrational.
Step-by-step explanation:
In the given sentences, 'each week' is employed as an adverb. Although it modifies a verb in both sentences, the meaning varies due to its placement near the different verbs. In the first sentence, it logically asserts that Marsha must save $10 per week to attain her goal of purchasing a new bike but in the latter sentence, the placement of the adverb 'each week' is unreasonable because 'buying a new bike every week with $10' is neither sensible nor logical. Thus, the placement of the word directly affects the sentence's meaning.