Table: montreal_boroughs
Columns: number_map
borough
population_canada_2011_census
area_in_km
density_per_km

Question: Which Density per km² is the lowest one that has a Number (map) smaller than 13, and an Area in km² of 11.1?
SQL: SELECT MIN("density_per_km") FROM montreal_boroughs WHERE "number_map" < 13 AND "area_in_km" = 11.1