Note: do not copy the answer, this type of question is already posted but i think that answer is not correct so kindly do not copy that answer.

Distribute the block of IP addresses in to 6 departments. First two gets 400 IP addresses each. Third department has 150 employees and 180 IP addresses are equally divided among last three departments. One of the IP address from the block is 10.1.2.3 /8. Which department the given IP address belongs to and how many IP addresses will be left for future use