A circle-shaped town has a population density of 5000(2-r) people per square kilometer at a distance of r kilometers from the center of the town (that is, it is more densely populated towards the center of town). a) Find the radius of the town assuming that the density is zero at the town limits. b) Write a Riemann sum that approximates the population of the town. c) Find the population of the town (don't use the Riemann sum for this).