Multiple Choice

I approached a coworker earlier this week and asked her, "Does our private student already have a copy of the new book, or are we bringing one to him tonight?"
She answered, "Yes."
"Yes what?"
"The second one."
"So why did you answer 'yes'?"
"Because in Japan, if you are given two choices, and say 'yes' you mean the second one."
"'A or B? Yes.' How can 'yes' be the second one?"
"It just is."
"So how do you say 'the first one'?"
"'The first one.'"
"Okayyyy...."

A day passed as I thought about this and then I asked her, "If 'yes' means the second one, what does 'no' mean?"
She was stumped.
After a long, contemplative pause, she replied, "I don't know. I don't think we ever say that when given two choices."
"So 'yes' is an sensible answer, but 'no' isn't?"
"Yes."

Coffee? Tea? Yes!