need to know if project is possible

Hello
i need to connect 2 sites A and B.
Main site is A with internet and network 10.1.1.1
B is a new site
A and B should be on the same network
So A and B are not visible.
I have relay antenna i can use of 30 metters called C
A and B are visible of C
A to C have 20 km
C to b gave 10 km
Should i do this :
A to C in point to Point
C to B in point o point
For this i have thought the configuarion
A will have RB433AH and 1 mini pci R52HN with 1 antenna 16 dbi sectorial of 60°, A will be in AP BRIDGE
C will have a rb433AH 2 mini pci R52NH and 2 antenna 16 dbi sectorial of 60°, one wlan will be in station pseudobridge to catch signal of A and second wlan will be in AP BRIDGE to give signal to B
B will have RB433AH ans 1 mini pci R52HN with 1 antenna 16 dbi sectorial, wlan will be configurer in station pseudobridge.

also should i work in 2.4 or 5GHZ?


what do you think about this configuration

Regards
Philippe