How to calculate the cross section from the interface of the QCD and EW diagrams

I am puzzled to get the cross section at the order of $\alpha_s\alpha^2$.
As we know, by executing the command (after including the b-quark in the proton)
MG5_aMC> generate p p > w+ b j QED=3 QCD=2
one will generate both order of $g_s^2 g_w$ and $g_w^3$ amplitudes.
I want to know in this case what the order of the cross section is.
If I only want to get the corss section at the order of $\alpha_s\alpha^2$, what should I do?
Best Regards,