true.

?- bad_density(Where, Density).
Where = united_states,
Density = 301139947/9826630 ;;
Where = argentina,
Density = 40301927/2766890 ;;
Where = kenya,
Density = 31987000/582650 ;;
Where = arcata,
Density = 15000/5.

?- less_pop(Place1, Place2).
40301927
301139947
Place1 = argentina,
Place2 = united_states ;;
31987000
301139947
Place1 = kenya,
Place2 = united_states ;;
31987000
40301927
Place1 = kenya,
Place2 = argentina ;;
15000
301139947
Place1 = arcata,
Place2 = united_states ;;
15000
40301927
Place1 = arcata,
Place2 = argentina ;;
15000
31987000
Place1 = arcata,
Place2 = kenya ;;
false.

?- halt.