Distribute the block of IP addresses into 6 departments. First two gets 400 IP addresses each. The third department has 150 employees and 180 IP addresses are equally divided among the 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.

Note: This needs to using VLSM Subnetting