Model extrusion coupling Help

Hi,
I need help in resolving an issue with my model. I have a number of ODEs of the form;
dA/dt = A + B domain 1
dB/dt = B+A-C domain 2
dC/dt = C+A domain 3
Each time I try to solve the problem, i keep getting a syntax expression error and I suspect that it is due to the fact that the dependent variables are domain restricted. Could someone tell me how to utilize extrusion coupling to make all the dependent variables present in all the domains? My model is attached herewith.

Thanks
Ene