The Admin, Sales and Warehouse are all correct. But the two servers are not. Why? because you will need a 3rd IP for the Router 2 interface facing the Switch 40. So 255.255.255.252 is not enough as a subnet mask. Try 255.255.255.248. You could also use a higher subnet mask for simplicity. It's NOT always a must to choose the BEST FIT mask unless you want to reserve the address range, it depends on the question you have. For example you can use a mask 255.255.255.0 for all the subnets Admin, Sales and Warehouse and the two servers. And make the changes only in the 3rd octet, like 192.168.1.0, 192.168.2.0, 192.168.3.0 and so on. This will make binary work simple.
For the serial link 172.16.1.4 - 172.16.1.3. The subnet mask 255.255.255.252 is OK. But the two IPs are on a different subnet since the 4 bit on the last octet is different in each IP. Try some thing like 172.16.1.9 - 172.16.1.10.
Remember that you also have another serial link in the network.
My idea is to restrict the number of hosts per network therefore there is more physical security I could also limit the ip addresses the dhcp server gives out so, however when computers are shut down the ip's become free again one way to sort this could be dynamic ip mac filtering.