The network in figure $3$ below has four segments located in four different computer rooms:

$($CR$1,$ CR$2,$ Cr$3,$ CR$4).$ Four network set$-$up scenarios presented below may be considered:

$1.$ Connecting the four computer rooms using a central switch within the same network.

$2.$ Defining a subnet for each computer room connected by central a switch.

$3.$ Defining a different network for each computer room connected by the central switch using four different VLANs.

$4.$ If you are connecting the four computer rooms using a router with a network for each computer room.

In each of the four scenarios above, discuss the following:

A$.$ Can computers from different computer rooms communicate with each other?

B$.$ What is the needed change $($if possible$)$ to make only one computer from the CR$1$ room connect to the network of CR$3?$

C$.$ Which device can be used as a gateway in each scenario.