Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What is the sum of Markatal, when Inhabitants Per Km² is less than 13, and when Area (in Km²) is 27?

### Inputs:
table_name: table, columns: ['Municipality', 'Population', 'Inhabitants per km²', 'Area (in km²)', 'Markatal', 'Island', 'Region']

### Response:
SELECT SUM Markatal FROM table WHERE Inhabitants per km² < 13 AND Area (in km²) = 27