$\left\{\begin{matrix}R=\frac{5c}{2eat}\text{, }&t\neq 0\text{ and }a\neq 0\text{ and }m\neq 0\\R\in \mathrm{R}\text{, }&\left(t=0\text{ or }a=0\right)\text{ and }c=0\text{ and }m\neq 0\end{matrix}\right.$

$\left\{\begin{matrix}a=\frac{5c}{2eRt}\text{, }&t\neq 0\text{ and }R\neq 0\text{ and }m\neq 0\\a\in \mathrm{R}\text{, }&\left(t=0\text{ or }R=0\right)\text{ and }c=0\text{ and }m\neq 0\end{matrix}\right.$