Choose the One Alternative That Best Completes the Statement or Answers

Multiple Choice

Choose the one alternative that best completes the statement or answers the question.
The Richter scale converts seismographic readings into numbers for measuring the magnitude of an earthquake according to this
function $$M ( x ) = \log \left( \frac { x } { x _ { 0 } } \right) , \text { where } x _ { 0 } = 10 ^ { - 3 } .$$
-What is the magnitude of an earthquake whose seismographic reading is 6.6 millimeters at a distance of 100 kilometers from its epicenter? Round the answer to the nearest tenth.

A) 2.8
B) 3.8
C) 2.5
D) 819.5