Funny you mention that! I learned that in Engineering Econ in 1971. Ten years later in my MBA econ classes, that distinction wasn’t made. I pointed it out in a paper and the prof that it was brilliant, that I had an excellent grasp of economics. It really bugged me that the difference wasn’t taught in 1981! And I’m not even sure my econ prof understood the difference.
That explains it.
I took econ in 1978 :) I got a B but never forgot the fundamentals.
Do they at least still draw an X?