Let $\overline{p}=\frac{\overline{b}\times \overline{c}}{\left[\overline{a}\overline{b}\overline{c}\right]}$, $\overline{q}=\frac{\overline{a}\times \overline{c}}{\left[\overline{a}\overline{b}\overline{c}\right]}$,$\overline{r}=\frac{\overline{a}\times \overline{b}}{\left[\overline{a}\overline{b}\overline{c}\right]}$ and $\overline{a},\overline{b},\overline{c}$  being any three non-zero, non-coplanar vectors then $\overline{p}.(\overline{a}+\overline{b})+\overline{q}.(\overline{b}+\overline{c})+\overline{r}.(\overline{c}+\overline{a})=$