There is a University that needs to create $3$ Networks for $3$ departments with $253$ Host addresses each. They need to design the address given to them which is $10\mathrm{.}0\mathrm{.}0\mathrm{.}0/8$ for the $3$ departments that would allocate $253$ Host addresses. Give $3$ Network addresses that they can assign to each department. How many usable host addresses can give to each department using the network addresses assigned? How many network addresses can they have based on the new subnet mask they computed? Why do we always subtract $2$ addresses from the useable host addresses?