Puzzle #76: Leaves

There are millions of leaves on your (or your parents’) lawn! OK, not really. Given:

1) The number of leaves is a four-digit number (abcd).
2) a times b equals d.
3) The digits are all different.
4) a plus b equals c.
5) Two of the digits are even, one digit is odd.
6) a equals 2.

How many leaves?

Submit your answer to Gene Wirchenko <genew@telus.net>. Your answer should be in the form of a proof. That means to show how your answer must be correct. The deadline is Wednesday, November 19, 2014 at noon Pacific Time. I will post the answer shortly after.