This almost looks like a homework question.
Very technically none of the answers are correct because they are being overly simplistic. When data is being constrained traffic is randomly dropped and the response to the lost traffic by the application varies a lot.
So if all 3 PC are streaming 1g of data though a 100m connection 2.9g of data must be discarded. It is completely random so it is impossible to predict how much any particular device gets. Realistically all three would in effect get no "usable" data through the connection because of the excessive discards.
Thanks Bill for reading my post.
In your case if I use a 10/100 WAN/LAN router instead of a 210 Mbps gigabit router, will be significant speed slow down for each computer? If so, why.
appreciate your comments.