On the Richter Scale, the Magnitude $R$ Of an Earthquake of Intensity

Multiple Choice

On the Richter scale, the magnitude $R$ of an earthquake of intensity $I$ per unit of area is given by $R = \log _ { 10 } \left( \frac { I } { I _ { 0 } } \right)$ where $I _ { 0 } = 1$ is the minimum intensity used for comparison. Find the magnitude $R$ (on the Richter scale) of an earthquake of intensity $I = 8,710,000$ Round to the nearest thousandth.

A) 8.940
B) 7.940
C) 9.940
D) 6.940
E) 3.940