An Internet Service Provider (ISP) has the following chunk of CIDR-based IP addresses available with it: 245.248.128.0/20. The ISP wants to give half of this chunk of addresses to Organization A, and a quarter to Organization B, while retaining the remaining with itself. Which of the following is a valid allocation of address to A and B?

Since half of 4096 host addresses must be given to organization A, we can set 12^th bit to 1 and include that bit into network part of organization A, so the valid allocation of addresses to A is 245.248.136.0/21 Now for organization B, 12^th bit is set to '0' but since we need only half of 2048 addresses, 13^th bit can be set to '0' and include that bit into network part of organization B so the valid allocation of addresses to B is 245.248.128.0/22