Its a quick sample how to configure this link. I'm wondering if you gateway will be your radio, but it's show
how to configure using 2 wireless interfaces in you point "MOUNTAIN" when your gateway is the radio.
To do this configuration, open a New Terminal using Winbox.
OFFICE 1 #LAN IP
/ip address add interface=eth1 address=172.16.16.1/22
/ip route add dst-address=0.0.0.0/0 gateway=x.x.x.x <- you need to define a default gatway, 192.168.0.2 if it goes to office 1 or 192.168.1.2 if goes to office 2