Hey everyone, I need to acquire an explanation concerning a question I encountered

with statistics. Here it is:

How many even numbers greater than 50000 can be made with the digits 3, 4, 5, 6, 7, 0 without repeating any of the digits?

The book lists the answer as 504 but I need an explanation as to how this answer is attained. If someone could explain it, I'd be very grateful.

Thanks.