Table schema:
CREATE TABLE table_name_47 (markatal INTEGER, inhabitants_per_km² VARCHAR, area__in_km²_ VARCHAR)

Question: What is the sum of Markatal, when Inhabitants Per Km² is less than 13, and when Area (in Km²) is 27?
SQL: SELECT SUM(markatal) FROM table_name_47 WHERE inhabitants_per_km² < 13 AND area__in_km²_ = 27