Hello Eunhye!

Here are my answers to your questions!

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1. 급여를 어느 정도 생각하고 계시나요?
I was wondering if the following sentence would work, too : What is your salary expectation? 

-> Yes definitely.

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2.
Your payment has not been received
The final installment was sent(remitted) last week

1) Do active voices work here too? (like the sentence below) or do passive voices change anything in nuance?

I have not received your payment
I sent the final installment last week

-> Here I think both active & passive usages sound perfectly fine.

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2) Can I use the word 'wire, transfer' for 송금하다?

-> In most cases you can. When it comes to banking terms, it is most likely certain words are dominantly used for certain actions. I think the expression “송금하다” (to another person) is most commonly said “to send money”.


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3. There is a claim against us regarding the product.

1) Can I say "There is a complaint against us regarding the product"?

-> Yes. Same meaning.

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2) and why don't we say more simply, "There is a claim against the product?"

-> I believe the meanings are roughly the same but the focus on the sentence is different (product vs us).


4. Please send us the catalog, the price list with the product guide.
Here "귀사 복사기" is missing
So, is this right? : Please send us the catalog, the price list with the product guide of your copiers (plural form)

-> Yes, although I think the meaning is most likely just implied.


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5. I am sending this letter to explore possibilities of future partnership.
Here,  is this 'the possibilities' or just 'possibilities?' (without 'the')
There was no 'the' in the subtitle but I heard 'the' when teacher Grace recapped in the latter part.


-> Both are fine. This is just another example of a trivial usage of “the” in English. I would personally put “the” but I don’t think it significantly changes the meaning even if you don’t put “the”.

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I hope this helps!

Best regards,

Mason U, CMI-Korean
Business Interpretation and Translation in Korean (BIT-K) Instructor