model {
   alpha0  ~ dnorm(0.0,1.0E-6);  # intercept
   alpha1  ~ dnorm(0.0,1.0E-6);  # seed coeff
   alpha2  ~ dnorm(0.0,1.0E-6);  # extract coeff
   alpha12 ~ dnorm(0.0,1.0E-6);
   tau     ~ dgamma(1.0E-3,1.0E-3);    # 1/sigma^2
   sigma  <- 1.0/sqrt(tau);
   for (i in 1:N) {
      b[i]         ~ dnorm(0.0,tau);
      logit(p[i]) <- alpha0 + alpha1*x1[i] + alpha2*x2[i] +
                     alpha12*x1[i]*x2[i] + b[i];
      r[i]         ~ dbin(p[i],n[i]);
   }
}
