How many four-digit numbers N = abcd satisfy all of the following conditions?
1. 4000 <= N < 6000
2. N is a multiple of 5.
3. N is not a mutlple of 3
Multiples of 5 = [ 5995 - 4000 ] / 5 + 1 = 400
Multiples of 5*3 = 15 = [ 5985 - 4005] /15 + 1 = 132 + 1 = 133
Number (mult of 5 but not a mult of 3)= 400 - 133 = 267
