China DOS Union

A company has been assigned a standard network segment address: 202.22.22.0
This company has 5 departments, with 20 to 25 computers in each department. The requirement is that the departments must not be able to communicate directly with each other. Each department should be on a separate subnet.
Work out these five subnets.
What I want to know is the method. Specifically how to calculate it, and I also need the answer.
If you were the one setting up the network, how would you do it.

5 departments? Then use 3 binary bits (that allows up to 8 departments) to distinguish the subnets. 11100000 = 224
So, the subnet masks are all: 255.255.255.224
00000000 = 0
00100000 = 32
01000000 = 64
01100000 = 96
10000000 = 128
10100000 = 160
11000000 = 192
11100000 = 224
First subnet: 202.22.22.0, IPs from 1 to 30, broadcast: 202.22.22.31
Second subnet: 202.22.22.32, IPs from 33 to 62, broadcast: 202.22.22.63
Third subnet: 202.22.22.64, IPs from 65 to 94, broadcast: 202.22.22.95
.... Got it now...
The subnet mask (netmask) is 255.255.255.224 for all of them