The Population Density X Miles from the Center of a City

Multiple Choice

The population density x miles from the center of a city is given by a function of the form $Q ( x ) = A e ^ { - k x }$ . Find this function if it is known that the population density at the center of the city is 9,000 people per square mile and the density 15 miles from the center is 6,000 people per square mile. Round numbers to six decimal places, if necessary.

A) $Q ( x ) = 3,000 e ^ { - 0.693147 x }$
B) $Q ( x ) = 9,000 e ^ { 0.693147 x }$
C) $Q ( x ) = 9,000 e ^ { 0.046210 x }$
D) $Q ( x ) = 9,000 e ^ { - 0.027031 x }$