I'm done my homework

[James A. Landau]

For a class I took in the fall of 1977, I interviewed an engineer at one of
the sewage treatment plants in the Washington DC metro area.  He complimented
me on being well prepared for the interview by saying "You've done your
homework".  I was already familiar with the phrase, and even recall it as being
moderately common, but this is the first usage I heard that I can nail down.

    - James A. Landau