How many four-digit numbers N = abcd satisfy all of the following conditions?
1. 4000 <= N < 6000
2. N is a multiple of 5.
So we have the multiples of 5 from 4000-5995.
Dividing each multiple of 5 by 5 we get 800-1199.
1199-800+1=400 multiples
+539 
