user: Question: For stellenbosch, which has a population larger than 155733, what is the average area?
Columns: ['Name', 'Seat', 'Population (2011)', 'Area (km 2 )', 'Density (inhabitants/km 2 )']
Types: ['text', 'text', 'real', 'real', 'real']
Sample row: ['Witzenberg', 'Ceres', 115946.0, 10753.0, 10.8]
SQL:

assistant: SELECT AVG("Area (km 2 )") FROM "Table" WHERE "Name" = 'stellenbosch' AND "Population (2011)" > 155733.0;