The 192.25.27.0 subnet should be assigned the subnet mask of 255.255.255.0 to accommodate 250 users. This subnet mask can accommodate a maximum of 254 hosts. The number of hosts that can reside on a subnet can be calculated using the formula 2n - 2 = x, where n is equal to the number of hosts bits in the mask and x is the resulting number of hosts. 2 is subtracted from the results to represent the two address, the network ID and the broadcast address, that cannot be assigned to computers in the subnet. Since the 255.255.255.0 mask leaves 8 bits at the end of the mask, the formula will be 28 - 2, which is 256 - 2, which equals 254.

In situations where the same subnet mask must be used for multiple interfaces on a router, the subnet mask that is chosen must provide capacity sufficient for the largest number of hosts on any single interface while also providing the equired number of subnets.

With a subnet mask of 255.255.255.128, the 192.25.27.0 subnet can accommodate only 126 hosts. The mask 255.255.255.128 leaves 7 host bits in the mask and when we plug that into the formula we get 27 - 2, which equals 126.

With a subnet mask of 255.255.255.224, the 192.25.27.0 subnet can accommodate only 30 hosts. The mask 255.255.255.224 leaves 5 host bits in the mask and when we plug that into the formula we get 25 - 2, which equals 30.

With a subnet mask of 255.255.255.252, the IP address 192.25.27.24 can accommodate only two hosts. The mask 255.255.255.252 leaves 2 host bits in the mask and when we plug that into the formula we get 22 - 2, which equals 2.