Find the product
(r31)(r18+r15+r12+r9+r6+r3+1)\displaystyle {\left({r}^{{3}}-{1}\right)}{\left({r}^{{18}}+{r}^{{15}}+{r}^{{12}}+{r}^{{9}}+{r}^{{6}}+{r}^{{3}}+{1}\right)}


Ans =