$$C=\frac{0.02413}{\log_{10}\frac{D}{r}}=$$
$C=\frac{2413\log_{\frac{D}{r}}\left(10\right)}{100000}$
$\left(D\neq r\text{ and }D>0\text{ and }r>0\right)\text{ or }\left(D\neq r\text{ and }D<0\text{ and }r<0\right)$
$D=r\times 10^{\frac{2413}{100000C}}$
$C\neq 0\text{ and }r\neq 0$
