subnet masks

Yes I should know these without thinking.

9 - 255.128.0.0
10 - 255.192.0.0
11 - 255.224.0.0
12 - 255.240.0.0
13 - 255.248.0.0
14 - 255.252.0.0
15 - 255.254.0.0

16 - 255.255.0.0
17 - 255.255.128.0
18 - 255.255.192.0
19 - 255.255.224.0
20 - 255.255.240.0
21 - 255.255.248.0
22 - 255.255.252.0
23 - 255.255.254.0
24 - 255.255.255.0

25 - 255.255.255.128
26 - 255.255.255.192
27 - 255.255.255.224
28 - 255.255.255.240

29 - 255.255.255.248
30 - 255.255.255.252
31 - 255.255.255.254
32 - 255.255.255.255