Q1.what is meaning of "private" ID with example?

Q2.how can i write private ID for class A,B,C>

Q3.important Q..Host need: mean subnet mask,how can i find it with two digit like example: 20

Q4. Network need: also i think want subnet mask, how can i find it with 5 digit

 

2811 Rouler19 *Any Private network ID *Class: C *Host Need is: Your last two digit in Your ID Server-PT DHCP 2960-24TT Switch PC-PT PC0 PC-PT PC1 *Any Private network ID *Class: B *Subnet: 255.255.255.0 - 2811 Router20 2960-24 Switch 1 Server-PT DNS *Any Private network ID *Class: C *Network Need is: 5 Server-PT Your website