Find R R = 2/3 log10 (1000-0.9)
$${\frac{{\mathtt{2}}}{{\mathtt{3}}}}{\mathtt{\,\times\,}}{log}_{10}\left({\mathtt{1\,000}}{\mathtt{\,-\,}}{\mathtt{0.9}}\right) = {\mathtt{1.999\: \!739\: \!305\: \!980\: \!944\: \!7}}$$