O2, CO2 and trees?

[Henri D Harness]

OK, I know trees come in all shapes and sizes, but I'm looking for a
fair general answer or a range to the following related questions:

1.  How much oxygen does the average tree produce?
2.  How much carbon dioxide does the average tree produce?

The sad fact is, I've read these numbers somewhere, but for the life
of me, I don't recall.  I'd much appreciate answers and, if possible,
sources.  It's become one of those questions that incessantly pesters
the mind.

I'd appreciate e-mail.

TIA