Updated: Question in GATE 2012 Computer Science and Information Technology

A question in GATE 2012 Computer Science and Information Technology has been updated:

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?

1. 245.248.128.0/21 and 245.248.128.0/22
2. 245.248.132.0/22 and 245.248.132.0/21
3. 245.248.136.0/24 and 245.248.132.0/21
4. 245.248.136.0/21 and 245.248.128.0/22