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

### Instruction:
What is the highest Markatal, when Municipality is Leirvík, and when Inhabitants Per Km² is greater than 79?

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

### Response:
SELECT MAX Markatal FROM table WHERE Municipality = leirvík AND Inhabitants per km² > 79