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 addresses to $A$ and $B$?
- $245.248.136.0/21 \text{ and } 245.248.128.0/22$
- $245.248.128.0/21 \text{ and } 245.248.128.0/22$
- $245.248.132.0/22 \text{ and } 245.248.132.0/21$
- $245.248.136.0/24 \text{ and } 245.248.132.0/21$
