Final answer:
To establish five subnets in a 132.45.0.0/16 network block, a minimum of three bits needs to be borrowed from the host portion, resulting in a subnet mask of 255.255.224.0 (/19).
Step-by-step explanation:
To create subnets within a network, you will need to borrow bits from the host portion of the IP address to use for the network's subnetting. The original network block assigned is 132.45.0.0/16, which indicates that the first 16 bits are the network part of the address, and we can use the remaining bits for subnets and hosts.
In order to subnet this address into at least five separate subnets, we must determine the minimum number of bits required. Since 2 to the power of 3 is 8, which is less than 5, it won't suffice; thus, we would need at least 2 to the power of 3 (which equals 8) to create our five subnets. However, since we need more than five, and 2^3 is only 8, we do not need to consider 2^4 which would yield 16 possible subnets. Therefore, we need only three (3) bits for subnetting to get at least five subnets. This will leave us with 13 bits for host addresses.
As a result of borrowing 3 bits for subnetting, our subnet mask changes from 255.255.0.0 (/16) to 255.255.224.0 (/19).