$${\mathtt{d}} = {\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{r}}$$ $${\mathtt{U}} = {\mathtt{d}}{\mathtt{\,\times\,}}{\mathtt{\pi}}$$ $${\mathtt{A}} = {{\mathtt{r}}}^{{\mathtt{2}}}{\mathtt{\,\times\,}}{\mathtt{\pi}}$$
$${\mathtt{c}} = {\frac{{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{V}}}{\left({\mathtt{a}}{\mathtt{\,\times\,}}{\mathtt{b}}\right)}}$$