F.4 AMaths

An earthquake occurs in city P. An expert finds that the magnitude of the earthquake (M) on the Richter scale of a place x km from city P is given by M=Ae^-0.007x, where A is a constant. The magnitude of an earthquake in city Q, which is 100 km from city P, is measured to be 4 on the Richter scale.


(a)Find the magnitude of the earthquake in city P on the Richter scale.
(b)Estimate the area of the region centered at P where the magnitude of the earthquake is 7 or above on the Richter scale. (Give your answer correct to the nearest 100 km^2)