Read the following conversation and answer the question.

M: Miss Smith, I told Dr. Brown that I would call him in the Houston office at ten o'clock by their time. Please find out the time difference for me so that I'll know when to place the call.

W: It's two hours earlier in Houston, sir. I know without looking it up because my sister lives there.

Question: When should the man place his call to Houston? 

- At 8:00.

- At 10:00.

- At 12:00.


At 8:00.