A zookeeper is monitoring the population of birds. The flock needs to have exactly three times more females than males to thrive, and the zoo only has room for a maximum of 20 male birds. Let x represent the number of male birds and y represent the number of female birds. Write the constraints to represent a thriving population of birds at the zoo. x > 0 and y > 0 0 < x ≤ 20 and y > 60 x > 0 and y < 20 0 < x ≤ 20 and 0 < y ≤ 60