Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_69 ( markatal INTEGER, municipality VARCHAR, inhabitants_per_km² VARCHAR )

### Question ###
What is the highest Markatal, when Municipality is Leirv k, and when Inhabitants Per Km is greater than 79?

### Accurate SQL ###

SELECT MAX(markatal) FROM table_name_69 WHERE municipality = "leirvík" AND inhabitants_per_km² > 79