The Richter scale is used for measuring the magnitude of an earthquake The Richter magnitude M is given by the model M 0 67log 0 37E 1 46 where E is the energy in kilowatt hours released by the earthquake Suppose an earthquake releases 18 500 000 000 kilowatt hours of energy What is the earthquake s magnitude to the nearest tenth a 7 4 b 7 5 C 8 1 d 8 05 OOOO