Chapter 8.6, Problem 50E

Population Density Of A City The population density (number of people per square mile) of a certain city is given by the function

$f(x,y)=\frac{50,000\left|xy\right|}{(x^2+20)(y^2\text{}+36)}$

where the origin (0, 0) gives the location of the government center. Find the population inside the rectangular area described by

R = {(x, y)|−15≤ x ≤ 15; −20 ≤ y ≤ 20}