Question Connect 3G modem/router to small business network

[SailBRO]

Work station "1" and "2" are located on top of building with good GSM reception. Idea is to use 3G modem/router, connected via LAN to non-controllable switch between station "1" and gateway/main switch, as access to internet, and using existing small business network to transfer internet to the ground floor. It is no way to make any changes to existing network, let’s say, I want nobody in the office will know, I'm using network for my purpose. My work station is "4". Is it possible to insert router TP-LINK TL-WR841N changed to be as a switch between my work station "4" and gateway/main switch (172.X.X.X)? As I understand, Wi-Fi access point (TP-LINK TL-WA860RE with lan connection) should be with default gateway to 3G modem/router (172.X.
X.X) and DHCP mode "OFF".

Available free 1 Ethernet port nearby station "1". No proxy, no VPN on network. All stations with static IP address and gateway to 172.X.X.X My internet, should not be visible to another stations, is it possible?

 

[Ralston18]

Two problems with your post:

1) Your post has the appearance of a homework question. We do not do homework for posters.

2) More seriously, you say "I want nobody in the office will know". That indicates that you are doing something very improper, unethical, stealing bandwidth, or just generally illegal.

I am going to delete the IP addresses you posted and close this thread.