key file in Print Exam

hnagahas's picture

I use "Answer" and "Solution" in the source file when creating exam.
I want to create out, key, sln files under Print Exam command.
What I write after "Solution" appears under xxx_sln.tex.
What I write after "answer" does NOT appear under xxx_key.tex.
In fact, xxx_key.tex has nothing in it.
How do I use key file?