CH：Amy, Are you guys going to lunch?
A：Yes. Would you like to join us?
A：I have to make one phone call before I leave. Would you like to wait for me or go ahead with everyone else?
A：Say, Chen Hao, my phone call can wait a few minutes. I need to tell you something while it is on my mind.
A：No, you said something wrong. Actually you said two things that caught my attention.
A：First, you used the expression "You guys."
A：I know they do, but that doesn't mean it's correct or polite.
A：Because the word "guy" is an informal term that refers to a man or boy. People today use the plural "guys" without regard for gender. That is not correct usage of the word and it demonstrates a lack of polish.
A：You could have simply asked, "Are you going to lunch?" Or you could have said, "Are you ALL going to lunch?"
A：Now please excuse me while I make that quick phone call. Otherwise we'll miss lunch altogether.
A：Yes. I have noticed that when someone says "thank you", your response is always "no problem."
A：Lots of people say that in response to "thank you." However, that is not the correct reply. The correct response to "thank you" is "You are welcome."
A：No, it's being polite and polished. "You guys" and "no problem" are slang phrases which are not formal.
A：That's right. Slang expressions will detract from your professional image. "You guys" is only acceptable with a group of men in a very informal setting like the locker room.
A：It is only acceptable when someone asks if you have problem with something.
A：You got it! Now let's eat. I am starving.