To create a Network Diagram and determine the critical path for the project, you need to follow these steps:

$1.$ Identify Tasks: Based on the information provided, the tasks could be:

$-$ Remove furniture

$-$ Paint room

$-$ Replace furniture

$2.$ Determine Task Dependencies: The tasks must be performed in the order listed above. You cannot paint the room until the furniture has been removed, and you cannot replace the furniture until the room has been painted.

$3.$ Estimate Task Durations: This will depend on your team's speed and efficiency. For example, if it takes $1$ hour to remove furniture, $8$ hours to paint a room, and $1$ hour to replace furniture, then each room will take $10$ hours to complete.

$4.$ Draw Network Diagram: Each task is a node in the diagram. Draw an arrow from each task to the tasks that depend on it$.$ For example, draw an arrow from "Remove furniture" to "Paint room", and from "Paint room" to "Replace furniture".

$5.$ Calculate Earliest Start $($ES$)$ and Earliest Finish $($EF$)$ Times: The ES for the first task is $0.$ The EF is the ES plus the task duration. For each subsequent task, the ES is the EF of the task it depends on$,$ and the EF is the ES plus the task duration.

$6.$ Calculate Latest Start $($LS$)$ and Latest Finish $($LF$)$ Times: The LF for the last task is its EF$.$ The LS is the LF minus the task duration. For each preceding task, the LF is the LS of the task it leads to$,$ and the LS is the LF minus the task duration.

$7.$ Identify Critical Path: The critical path is the sequence of tasks that has the longest total duration. Any delay in these tasks will delay the project.

In this case, since all rooms are the same and tasks for different rooms can be performed in parallel, the critical path is the sequence of tasks for a single room. The total project duration will be the duration for a single room times the number of rooms, divided by the number of teams you have, assuming each team can work on a different room at the same time.