user: Question: What is the lowest Population per km² (2009) that has a solomon islands province, with an Area (km²) smaller than 28400?
Columns: ['Province', 'Capital', 'Area (km²)', 'Population census 1999', 'Population per km² (2009)', 'Population census 2009']
Types: ['text', 'text', 'real', 'real', 'real', 'real']
Sample row: ['Central Province', 'Tulagi', 615.0, 21577.0, 42.4, 26051.0]
SQL:

assistant: SELECT MIN("Population per km² (2009)") FROM "Table" WHERE "Province" = 'solomon islands' AND "Area (km²)" < 28400.0;