\begin{Schunk}
\begin{Sinput}
 bs <- coef(m2)
 yhatmean <- bs[1] + bs[2] * mean(dat$x1) + bs[3] * mean(dat$x2) + bs[4]*mean(dat$x1)*mean(dat$x2)
 yhatmean
\end{Sinput}
\begin{Soutput}
(Intercept) 
   1281.753 
\end{Soutput}
\end{Schunk}
