Computer Network Class c network Division subnet

Computer Network Class c network is divided into subnets a unit has a class c network 200.1.1, it has four departments, the number of hosts are 72 in Department a, Department B 35, Department c 20, divide 18 hosts in department d into subnets: (1) give a possible subnet division and its subnet mask www.2cto.com (2) if the number of hosts in department d increases to 34, is this solution feasible? What should I do? C-type network default subnet mask 255.255.255.255.02 ^ N-2> = 72 N minimum value is 7 then subnet mask is 255.255.255.255.128 host address on 200.1.1.1 to 200.1.1.127 Similarly, department B 35, 255.255.255.192. host addresses: 200.1.1.129 to 191; host addresses: 200.1.1.193 to 200.1.1.223; Department 18. host address 200.1.1.225 to 200.1.1.254 if host D is increased to 34, it is clear that the network address is not 200.1.1.225 to 200.1.1.254, so you have to increase the address.