$\left\{\begin{matrix}H=\frac{3v}{nr^{2}}\text{, }&r\neq 0\text{ and }n\neq 0\\H\in \mathrm{R}\text{, }&\left(n=0\text{ or }r=0\right)\text{ and }v=0\end{matrix}\right.$

$\left\{\begin{matrix}n=\frac{3v}{Hr^{2}}\text{, }&H\neq 0\text{ and }r\neq 0\\n\in \mathrm{R}\text{, }&\left(r=0\text{ or }H=0\right)\text{ and }v=0\end{matrix}\right.$