$R=5chm\text{ and }5chm=12cm$

$\left\{\begin{matrix}m=0\text{, }&\left(h=0\text{ or }c\neq 0\right)\text{ and }R=0\\m=\frac{R}{12c}\text{, }&h=\frac{12}{5}\text{ and }c\neq 0\\m\in \mathrm{R}\text{, }&R=0\text{ and }c=0\end{matrix}\right.$

$\left\{\begin{matrix}h=\frac{R}{5cm}\text{, }&R=12cm\text{ and }m\neq 0\text{ and }c\neq 0\\h\in \mathrm{R}\text{, }&\left(c=0\text{ or }m=0\right)\text{ and }R=0\end{matrix}\right.$