An organization is granted a block of addresses with the beginning address 16.13.64.0/24. The organization needs to have three subblocks of addresses to use in its three subnets: one subblock of 28 addresses, one subblock of 63 addresses, and one subblock of 120 addresses. Design the subblocks.

The organization has been granted a block of addresses starting from 16.13.64.0/24. This means that the organization has 256 addresses to use (from 16.13.64.0 to 16.13.64.255).

The organization needs to divide this block into three subblocks: one with 28 addresses, one with 63 addresses, and one with 120 addresses.

To design the subblocks, we need to find the subnet mask for each subblock. The subnet mask is determined by the number of addresses in the subblock.

1. For the subblock with 28 addresses, the closest power of 2 is 32 (2^5 = 32). So, the subnet mask for this subblock is /27 (32 - 5 = 27). The range of addresses for this subblock is 16.13.64.0 to 16.13.64.31.

2. For the subblock with 63 addresses, the closest power of 2 is 64 (2^6 = 64). So, the subnet mask for this subblock is /26 (32 - 6 = 26). The range of addresses for this subblock is 16.13.64.32 to 16.13.64.95.

3. For the subblock with 120 addresses, the closest power of 2 is 128 (2^7 = 128). So, the subnet mask for this subblock is /25 (32 - 7 = 25). The range of addresses for this subblock is 16.13.64.96 to 16.13.64.223.

So, the three subblocks are:

• 16.13.64.0/27 (28 addresses)
• 16.13.64.32/26 (63 addresses)
• 16.13.64.96/25 (120 addresses)

The organization has been granted a block of addresses starting from 16.13.64.0/24. This means that the organization has 256 addresses to use (from 16.13.64.0 to 16.13.64.255).

The organization needs to divide this block into three subblocks.

1. The first subblock needs 28 addresses. The smallest subnet that can accommodate this is a /27 subnet, which provides 32 addresses. So, the first subnet will be 16.13.64.0/27, which includes the addresses from 16.13.64.0 to 16.13.64.31.

2. The second subblock needs 63 addresses. The smallest subnet that can accommodate this is a /26 subnet, which provides 64 addresses. However, we can't start this subnet at 16.13.64.32 because that address is already included in the first subnet. So, we start this subnet at the next available address, which is 16.13.64.32. So, the second subnet will be 16.13.64.32/26, which includes the addresses from 16.13.64.32 to 16.13.64.95.

3. The third subblock needs 120 addresses. The smallest subnet that can accommodate this is a /25 subnet, which provides 128 addresses. We can't start this subnet at 16.13.64.96 because that address is already included in the second subnet. So, we start this subnet at the next available address, which is 16.13.64.96. So, the third subnet will be 16.13.64.96/25, which includes the addresses from 16.13.64.96 to 16.13.64.223.

This leaves us with a remaining block of addresses from 16.13.64.224 to 16.13.64.255, which can be used for future expansion.