Q3. (a) An ISP is granted a block of addresses with a network address of 162.173.184.0/21. The ISP needs to allocate 500 addresses for three organizations, 250 addresses for one organization, 60 addresses for two organizations, and 30 addresses for three organizations. Determine the range of addresses for each organization and the range of unallocated addresses. Also, give the subnet mask for each sub-network. (10 marks)