Question : white listing IPs that end in 0/22

Hi, I'm writing an internet program that only certain networks are allowed to view. I got the list of IP addresses to white list in our database but I'm a coder and not an admin. The IP list they gave me look like this:

201.52.121.0/22

(I changed the IP to something random to protect my client's network, but that's the ending octet)

I'm not sure what range of IPs this actually encompasses. Can someone tell me? Because at first I thought this meant that the IPs I was supposed to white list were

201.52.121.0 - 201.52.121.22.

but apparently that's incorrect.

Also another one has an ending octet of 64/28

Not really sure what the range on that is actually supposed to be

Answer : white listing IPs that end in 0/22

google subnet calculator
example
http://www.subnet-calculator.com/subnet.php
put the address then the bit.  
/22 is class b
/28 is class c